







4 digit "combinations" 
20180518 

Marvin pose la question : I am designing a game, and I need away of figuring this out without having to write numerically all these numbers
4 digit combinations 0 through 13 nonrepeating Penny Nom lui répond. 





Four multiples of 10 
20170923 

Laudacir pose la question : Four multiples of 10 are added together.the total is a 3 digit number with three consecutive digits. What could the four number be? Penny Nom lui répond. 





Significant digits 
20170806 

Pat pose la question : The directions for a problem are: "Solve the problem, expressing your answer
using the correct number of significant figures."
Problem
0.0043 divided by 2.04
Answer before using the correct number of significant figures is
0.002107843
Is the correct number of significant figures the number below?
2107843
Pat Penny Nom lui répond. 





4 digit codes with repeating digits 
20170601 

Morgan pose la question : what are all possible 4 digit code repeating numbers? cuz i know that you have one website on it but, it doesn't repeat 2 numbers in a code. Harley lui répond. 





Four digit numbers 
20160908 

ning pose la question : 00009999 there is ten thousand 4digit numbers. How to find the number of ways that 4 digit are the same? How to prove it by using formula? Penny Nom lui répond. 





The tens digit of a number is five times the unit digit 
20160519 

sanjeev pose la question : The tens digit of a number is five times the unit digit. Find the number? Penny Nom lui répond. 





A six digit code 
20160506 

Ralph pose la question : How many combinations are possible if a "safe" has four buttons and you can use a six digit code? (these are just single press buttons..)For example, this could be one possible combination: Button 4 Button 1 Button 1 Button 3 Button 2 Button 4. Thanks! Penny Nom lui répond. 





The last two digits of a phone number 
20160403 

Joshua pose la question : I want to find the last two digits of a phone number whose first eight numbers of a ten digit phone numbers are known. Penny Nom lui répond. 





Missing digits in a phone number 
20150107 

Janelle pose la question : I had a friend try and play a game on me, regarding phone numbers, so I only know the area code , and the last four digits of the phone number. Which means, there are 3 digits that I need to figure out all the possibilities to. Penny Nom lui répond. 





Four digit phone numbers 
20140225 

Tom pose la question : Hi, I'm an online math teacher, working on lessons for my students.
This question is in their book and I can't do it...! Help!
It has to do with phone numbers, and in this problem,
we are only dealing with
the last 4 digits of the number.
It asks how many possible numbers we have
if at least one digit repeats in the last 4 digits of the number. Penny Nom lui répond. 





A number with all the digits different 
20140207 

Jon pose la question : I'm not a mathematician but just curious. Is there a name for a number of up to ten digits where each digit is different,
i.e the equivalent of an isogram in linguistics? My online banking gives me a random 8digit number each time I log on
and it is rare to get one of the type I refer to. There must be calculable odds, but I'm only allowed one question!
Thanks in advance
Jon Harley Weston lui répond. 





A 4 digit number 
20131220 

swathi pose la question : How many 4 digit numbers can be formed using the digit 3 only once but the digit 3 must be used in all numbers? Penny Nom lui répond. 





A 2digit number 
20130513 

A teacher pose la question : Find a “2digit number” where the sum of the 1st digit (on the Left)
and the square of the 2nd digit equal the same number. Lorraine Dame, Harley Weston lui répond. 





A 4 digit code 
20130326 

chris pose la question : I saw a previous question about a 4 digit code type thing and I was wondering if you could email me that same type of thing.
I changed the pin number on my phone's lock screen and I tried hard to remember it, then I had to go help my mom with something and I automatically forgot it and there is no way for me to get back on my phone.
I need all of the possible 4 digit number combinations without the numbers 0, 1, or 2. It cannot be repeating, ascending, or descending.
I know you may not want to do all of them, but I really need it. Robert Dawson lui répond. 





A 3 digit number puzzle 
20130311 

Bonnie pose la question : My number has 3 digits. My number is not a multiple of 100. My number is a multiple of 50. My number is a factor of 1000. What is my number? Penny Nom lui répond. 





Four digit "combinations" using 0124 
20130227 

Ayana pose la question : What are all the possible four digit combinations using 0124. Please list them for me. Thank you. Penny Nom lui répond. 





A 4 digit phone lock using the digits 4, 2, 3 and 0 
20121224 

Ragu pose la question : I would like to know formula for searching a combination of 4 digit. eg.
I knew my Phone Lock combination is my car plate number 4230. But
this time, i used another way around instead of 4230.
But I am sure, there is only this 4 digits only. 4 & 2 & 3 & 0 Penny Nom lui répond. 





The last 4 digits of a cell phone number 
20121222 

Jacob pose la question : If the last 4 digits of a cell phone number, XXXXXXABCD, are restricted where: A cannot be 0 or 1 and B cannot be 0 / how many possible 4 digit combinations are left? Penny Nom lui répond. 





Some 6 digit numbers 
20121023 

Mason pose la question : How many different 6 digit numbers can you make using the digits 1 ,2 5, 6, 7, and 9? How many of these sixdigit numbers are divisible by 6? Penny Nom lui répond. 





4 digit combinations 
20121017 

Scott pose la question : How many different 4 number combinations from 0123456789 with 2 out of the 4 odd and 2 out of the 4 even, with no numbers repeating. Thanks p lui répond. 





A 2digit number 
20120823 

patty pose la question : Write the 2digit number that matches the clues.
My number has a tens digit that is 8 more than the ones digit. Zero is not one of my digits.
My number is Penny Nom lui répond. 





A 4 digit number 
20120809 

May pose la question : The number is given as ABCD. The first digit is a quarter of the last digit. The second digit is one less than the first digit.
When the number ABCD is multiplied by four its digits appear in the reverse order. None of the digits are the same. What is the number. Pleas help because my child need help and I can not do this. Thank you. Penny Nom lui répond. 





Mr. Schneider's mass 
20120229 

Khiya pose la question : Mr. Schneider's mass is 2 digits. The first digit is 3 times the second digit. Both digits are odd numbers, and his mass is greater than 35 kg. What is Mr. Schneider's mass? Penny Nom lui répond. 





Can the result of the calculation be 2? 
20120209 

Thomas pose la question : You have the digits 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9 in a random order side by side and put randomly between two digits a colon, so that a division comes into existence. Can the result of the calculation be 2? Robert Dawson and Chris Fisher lui répond. 





A two digit number 
20120129 

Christine pose la question : Five times the sum of the digits of a two digit number equals the number. If the digits are reversed, it becomes nine more than the original number. What is the original number?
I really don't understand this question, help me please Penny Nom lui répond. 





The number of digits in a number base m 
20111222 

Jash pose la question : Assume there is a number system of base m.
The one property of this system is: If 2 numbers written in this system, which have 'a' and 'b' as the number of digits are multiplied, then the product of the 2 numbers will have a number of digits which is a function f(a,b).
In other words, as long as the number of digits of the 2 numbers are constant, the number of digits of their product is a constant.
Find m. Robert Dawson lui répond. 





Rounding 
20111214 

seth pose la question : A decimal number rounded changed to 23.7 after it was rounded.
Give a decimal number that is less than 23.7 and another that is greater than 23.7 that each round to 23.7.
Explain to what place each number was rounded. Penny Nom lui répond. 





3digit, daily numbers 
20110929 

Margaret pose la question : I need the list/group for a raffle that would contain the combinations
for a 3 digit (000999) daily number. There would be 100 tickets sold
with 10 3digit numbers from each numerical group beginning
from 000's, 100's 200's, 300's,...900's. No duplicates/replacement. What would be the
list of possible combinations of each group of 100 tickets, keeping each
different group/list of combinations in separate blocks of 100 tickets
without duplication. So I could use 1 list of 100 this year and the next list of
combos next year and so forth. Please help!
Example: 000,197,245,367,445,569,618,777,842,964
What would be the possible lists of each 100 tickets?
Thank you Penny Nom lui répond. 





A number less than 100 
20110917 

Sharon pose la question : I am a number less than 100. My ones digit is 6 the sum of my digit is 11. What sum am I? p lui répond. 





A four digit number 
20110916 

gina pose la question : i am having a hard time figuring this out.. i believe the answer is 3105 but the 0 is throwing me off... i am a 4 digit number between 3100 and 3200, none of my digits are even, the sum of my digits is 9, the largest digit is in the ones place, what number am i ?? Penny Nom lui répond. 





A two digit number 
20110826 

Felicia pose la question : Write the 2digit number that matches the clues.
My number has a tens digit that is 8 more than the ones digit.
Zero is not one of my digits Penny Nom lui répond. 





What is the 6001st digit that Sam wrote? 
20110215 

Sarah pose la question : Sam wrote the natural numbers from 1 to 5280 in order. What is the 6001st digit that Sam wrote? Penny Nom lui répond. 





Reversing the digits 
20110208 

rejie pose la question : if the digits are reverse , the number is 9 less than the original number.what is the equation? Penny Nom lui répond. 





Four digits are to be randomly selected 
20110120 

sarahbear pose la question : Suppose four digits are to be randomly selected (repetitions allowed) Find the probability that
A. 5562 is selected
B.0000 is selected
C. All four digits are the same
D. 2 is the first digit selected Penny Nom lui répond. 





A product of 1 000 000 
20101119 

Sharron pose la question : There are many pairs of numbers that when multiplied together give a product of 1 000 000. However, there is one pair, and only one pair, of whole numbers that contain no zero digits and has a product of 1 000 000. What are these two numbers? Stephen La Rocque lui répond. 





What numbers can I be? 
20101113 

john pose la question : my thousands digit is 2 times my ones digit.my hundreds digit is my ones digit plus 2. my tens digit is the difference between my thousands and hundreds digit what numbers can i be? Penny Nom lui répond. 





Choose any three digits that are less than ten 
20100912 

cecille pose la question : my son have a homework, but i don't understand the question. here's the problem:
choose any three digits that are less than ten.
make all the two digit number you can using those three digits.
add up the two digit numbers you created and divided by the
sum of the original three digits.
record your answer. then do it again with another three digits. write your observation about
the answer. Claude Tardif lui répond. 





Numbers that can be formed using the digits 1,2,3,4,5,8,9 
20100719 

Donessa pose la question : write the number that is 2000 more than the difference between the largest and the smallest
number that can be formed using the digits 1,2,3,4,5,8,9 Tyler Wood lui répond. 





Two problems 
20100527 

debbie pose la question :
Question from debbie, a parent:
hi, i have a daughter and she asked me a maths question I cannot solve. I was just wondering if you can give me the answers plus the working out so I could explain to my daughter,
1. The leftmost digit of a sixdigit number N is 1. If this digit is removed and then written as a rightmost digit, the number thus obtained is three times N .Find N.
2. Four friends are racing together down a flight of stairs. A goes 2 steps at a time, B 3 steps at a time. C 4 steps at a time and D 5 steps at a time. The only steps which all four tread on are the top one and the bottom one. How many stairs in the flight were stepped on exactly once? Penny Nom lui répond. 





Four digit numbers 
20100522 

tyeisha pose la question : Whats all the four digit numbers you can come up with using numbers 09 Tyler Wood lui répond. 





Odd numbers with no repeated digits 
20100501 

jameka pose la question : How many odd numbers can be written from the set {2,3,4,5,6} if no digits may be used more than once? Penny Nom lui répond. 





How many zeros? 
20100318 

jeff pose la question : 1 light yr is 6,500 billion miles, the galaxy "Andromeda" is 2,500,000 million light yrs, how many zeros are in this equation ? Robert Dawson lui répond. 





A code on my pedometer 
20100219 

Jacqui pose la question : Hi I need to break a code on my pedometer. I have only 3 digits 1 2 and 3 but need to fill a 5 digit code. I have tried to find answers but they seem to relate to if the digits are only used once. I can use them in any order and repeated as many times. How many possibilities are there and is there an easy way to run through them. Many thanks Tyler Wood lui répond. 





4digit positive numbers 
20100215 

marjon pose la question : Find the sum of all the 4digit positive numbers with no zero digit. Penny Nom lui répond. 





Three digit odd numbers 
20100204 

Rebecca pose la question : Question from rebecca, a student:
how many three digit odd numbers can be formed using the digits 1,2,3,4,5,6 without using any digit more than once? Tyler Wood lui répond. 





A 4digit phone code 
20100121 

pat pose la question : my daughter can`t remember her 4digit code to unlock her phone. she is pretty sure it starts with a 4. can you help us? my brain is locked up Robert Dawson lui répond. 





A place value problem 
20091129 

Ivy pose la question : My tens digit is 4 less than my thousands digit. My ones digit is twice my tens digit. My ten thousands digit is one less than my ones digit. My hundreds digit is the sum of my tens and thousands digit. My thousands digit is 6. Penny Nom lui répond. 





Jill and Bill 
20091104 

Lisa pose la question : Jill and Bill are two members of the Hill family. Jill is 8 years old and Bill is 9 years old. What will Bill's age be when the total of the digits in both their ages is once again 17? Stephen La Rocque lui répond. 





In what order are the following digits? 
20090930 

Jewell pose la question : In what order are the following digits?
0,2,3,6,7,1,9,4,5,8 Penny Nom and Claude Tardif lui répond. 





The sum of digits of 4444^4444 
20090831 

SHIVDEEP pose la question : The sum of digits of 4444^4444 is A .The sum of digits of A is B .
Find the sum of digits of B ? Claude Tardif lui répond. 





Unlocking my suitcase 
20090821 

Jamboree pose la question : I need to have all the possible combination of three digit between 09, i have seen the answer that there are 720 combination are there. Could you please show me all those combination numbers so that i could try it out to unlock my suitcase, will you please write it down all those combination and send it to me Victoria West lui répond. 





A number puzzle 
20090517 

Gita pose la question : Ok, we really need help for a homework problem due on Monday morning
I've been trying for 2 hours and can't figure it outif I can't I'm not sure
how my son can....We've been given a puzzle with the following rules:
The sum of each side must equal 15
We can only use the numbers 1,2,3,4,5,6,7, 8
A number can be used only once
(Hint: Think of all combinations of 3 numbers = 15)
The puzzle looks like this:
_____ _______ ______
_____ ______
_____ _______ ______ Penny Nom lui répond. 





7 digit combinations 
20090511 

CAROL pose la question : I NEED TO KNOW HOW MANY 7 DIGIT COMBINATIONS FROM 09 THERE ARE WITHOUT ANY REPEATES,
OR WHAT THOSE COMBINATIONS ARE? Penny Nom lui répond. 





Combinations and permutations 
20090507 

Renee pose la question : We are trying to figure out the equation or how to solve the problem of how many combinations of 4 digits you can get out of 09 without repeating the numbers in a set (i.e., no 0001, 0002) begining with 0123, 0124, 0125 etc
Thanks! Stephen La Rocque lui répond. 





Fourdigit combinations 
20090418 

Carri pose la question : How many 4digit combinations can be made out of digits 1, 2, 3, 4, & 5 using each number once? What are the combinations? Penny Nom lui répond. 





How many times is 9 in pi? 
20090409 

Serena pose la question : How many times is 9 in pi? Robert Dawson lui répond. 





A 5 digit push combination lock 
20090404 

Andrew pose la question : I have a 5 digit push combo lock that i forgot the combo for. it has numbers 14 and each number can be pressed more then once ie. 11111, 36356
is there an algorithm out there that will list out the possible combinations for me? or maybe a way i could write them out myself. Penny Nom lui répond. 





0123456789 
20090325 

Dr. pose la question : Many years ago I discovered that there are 33 numbers which,
when multiplied by 0123456789, simply rearrange the digits. Surprisingly
(to me at least) is the fact that the digits of all of those 33 numbers add up
to one of the 6 "cardinal" numbers 1, 2, 4, 5, 7, and 8. For example
6 + 2 = 8 and 62 X 0123456789 = 7654320918 etc.
Another interesting (to me) fact is that only the cardinal numbers
1, 2, 4, 5, 7, and 8 rearrange the digits in the number 9876543210.
My question is: "Is this known to anyone but me and the people I have
told?" Robert Dawson lui répond. 





4 digit numbers from 1159 
20090310 

David pose la question : I have the digits "1159" and need to come up with a complete list of possible fourdigit combinations. It does NOT matter the order of the two number ones (1), so this will help eliminate many possibilities.
Separately, it would also help to actually know the actual number of combinations with which I am dealing to start.
David :) Penny Nom lui répond. 





Four digit numbers 
20090310 

Theresa pose la question : I need to know the number of 4 digit numbers that can be formed using 1234 without repeating numbers Penny Nom lui répond. 





4 digit strings starting with 7 
20090303 

Angel pose la question : I need to no all the 4 digit combinations starting with 7 and with no repititions. Penny Nom lui répond. 





The page numbers in a book 
20090210 

Nichole pose la question : It takes 852 digits to number the pages of a book consecutively. How many pages are there? Penny Nom lui répond. 





Dividing the digits 1  9 into two groups 
20090209 

donna pose la question : using the numbers 1 to 9 can you arrange these into 2 groups, both of which have the same total, and no you cant turn the 6 upside down Penny Nom lui répond. 





4 digit arrangements of 7 3 6 6 
20090205 

Carole pose la question : I need all the four digit combinations using the numbers 7 3 6 6 Penny Nom lui répond. 





Missing three digits in a phone number 
20090130 

Elmer pose la question : I have part of a phone number. the first 3 digits are 212, the last digit is four, and the three missing digits are all odd, how many numbers will I have to call to get the right number?
212 _ _ _ 4? Stephen La Rocque and Penny Nom lui répond. 





Four digit numbers using 1, 0, 2 and 8 
20090127 

Mike pose la question : How many combinations of this four digit number 1028 can this produce only using those numbers. Example would be 0000, 0001,0002,0008,0010,0011,0012,0018,etc... Penny Nom lui répond. 





Three consecutive natural numbers 
20090126 

abby pose la question : 1.what is the smallest fourdigit number that is the sum of the three
consecutive natural numbers? what are the three consecutive
natural numbers that give this sum?
2.what is the largest three digit number whose square root is a prime? Penny Nom lui répond. 





The tens digit of 0! + 1! + 2! + 3! + 4! .............+9999! + 10000! 
20090123 

Kaylyn pose la question : determine the tens digit for the expression:
0! + 1! + 2! + 3! + 4! .............+9999! + 10000! Robert Dawson and Penny Nom lui répond. 





A three digit number 
20090120 

marcha pose la question : when this three digit number is rounded to the nearest ten, the sum of its digits
is 16 the hundreds digit of this number is 8 and the ones digit is 5, what is the number? Robert Dawson lui répond. 





A four digit passcode 
20090112 

john pose la question : i have a machine at home that has a four digit passcode and the numbers range from 1 to 4 how can i get all the ways those numbers can be used Harley Weston lui répond. 





The 2 rightmost digits 
20081218 

Peter pose la question : Is there a pattern for the 2 rightmost digits of a power? For example, one problem for a math competition was what are the 2 rightmost digits of 3^1993? Robert Dawson and Victoria West lui répond. 





Student who is inverting digits 
20081209 

Tammie pose la question : Do you have any strategies for addressing inversion of digits in two digit numbers. For example  The student the teacher is working with will write "14" and the number is 41. She has tried highlighting, practice writing numbers, and hundreds charts and finding patterns. Help! Thank you! Robert Dawson and Victoria West lui répond. 





I am a whole number less than 100 
20081203 

Cecelia pose la question : If I am a whole number less than 100
and the sum of my digits is 4
and half of me is an odd number
What number am I?
Also am I prime or composite? Penny lui répond. 





A 4 digit number 
20081106 

Chris pose la question : numbers 0  9 form a 4 digit number with no repetition.
It would round to 3000 if rounded to the nearest thousand
The digit in the tens place is twice the value of the digit in the thousands place.
It is an odd number.
It contains the largest digit.
It contains one digit less than 2.
The digit in the hundreds place is odd.
Can you find the 2 numbers? Penny Nom lui répond. 





4 digit combinations 
20081105 

Laura pose la question : I need to know all the number combinations possible with a 4 digit combination with double zero in the middle??? Penny Nom lui répond. 





What is the exact value of pi? 
20080927 

mahesh pose la question : what is the exact value of pi.
22/7 is accurate value of pi, if not then how can i find out the exact pi value. Harley Weston lui répond. 





Repeating fractions 
20080909 

Juli pose la question : My teacher recently put my math class to the test...
We were deiscussing repeating fractions and she asked
us to find out what the bar over a repeating decimal is called. I found out
it was called the vinculum. But she also said to find out what the number
under the vinculum was called. I can't seem to find it anywhere. Penny Nom lui répond. 





Hundreds, tens, and units digits 
20080905 

Cynthia pose la question : write an expression for the value of a threedigit number whos hundreds, tens, and units digits are x, y, and z, respectively Penny Nom lui répond. 





3 digit combinatios from 09 
20080727 

Mike pose la question : I need to know all the possible 3 digit combinations using the numbers 09.
The numbers can be repeated as long as they are not of the same set.
Example for not repeating: 123 is ok but not 321 or 231,132,213, etc.
Please help me. Thanks, Mike. Stephen La Rocque lui répond. 





Sum of Digits 
20080724 

Warren pose la question : If 100^2525 is written in decimal notation, what is the sum of digits? Penny Nom lui répond. 





The number of digits in a really big exponent 
20080721 

Pete pose la question : how would you find the number of digits in a really big exponent without a calculator? Penny Nom lui répond. 





The sum of the digits of twodigit number is 9 
20080701 

Audrey pose la question : the sum of the digits of twodigit number is 9. if the digits are reversed, the new number if 63 greater than the original number. find the number. Penny Nom lui répond. 





A 7digit odd number 
20080626 

Godryk pose la question : I am the smallest 7digit odd number. my ones digit is the sum of my thousands, and ten thousands digits. What number am I? Penny Nom lui répond. 





111...111 * 2003 
20080623 

Peggy pose la question : Number a = 111...111 formed by 2003 1's. Find the sum of the digits of the number 2003 * a. Penny Nom lui répond. 





The sum of the digits of a number 
20080623 

Ben pose la question : Question: Using mathematical induction, prove that if the sum of the digits of a number is divisible by three, then the number itself is also divisible by 3. Penny Nom lui répond. 





A 6 digit number 
20080423 

rajiv pose la question : write the smallest 6digit number using three different digits with 6 in the ten thousands place and 1 in the hundreds place Penny Nom lui répond. 





Rearrangements of the digits in 0123456789 
20080323 

Joe pose la question : Found a close problem but not quite.
Using digits 0123456789, how can I figure what all the different
possibilities would be without repeating any digits?
I know that there are 10! possible answers but how can I figure out what
they are? Stephen La Rocque lui répond. 





A 4 digit passcode 
20080216 

Rob pose la question : If there is a 4 digit passcode with only 6 punch in symbols, how many possibilities are there and what are they?
symbols are: Y, X, RB, RT, LB, LT. Please get back to me, thanks for your time and help. Stephen La Rocque lui répond. 





Five digit combinations 
20080215 

Debbie pose la question : I would like to get a list of all the possible 5 digit combinations of the numbers 12345. Penny Nom lui répond. 





A 2 digit number 
20080213 

Jenny pose la question : The units digit of a certain twodigit number is one more than 4 times the tens digit.
The number formed by interchanging the digits is 6 more than 3 times the original number.
Find the original number. Penny Nom lui répond. 





7, 6, 5, 4, 3 and 2 digit numbers 
20080210 

Edward pose la question : using the number 12345678 how many 7, 6,5,4,3 & 2 digit numbers can you make when not using any number twice in the same number Penny Nom lui répond. 





A positive integer with 2007 digits 
20080206 

Tom pose la question : Prove that there's a unique positive integer of 2007 digits lenght, divisible by 2^2007, and made up solely by the digits 2 and 5. Penny Nom lui répond. 





A math riddle 
20071127 

Kathleen pose la question : My 4th grade daughter was given a math riddle which she is expected to answer using a problem solving strategy. The question is:
The number of my hundreds and the number of my thousands is 3. The number of my tens is 7 times the number of my thousands. All my digits are different. What am I?
I have tried to come up with an answer, but am beginning to think it is less complicated than what I have come up with. Stephen La Rocque lui répond. 





Using the digits 1 to 9 
20071120 

sunjoo pose la question : write the least whole number that uses the digits 1 though 9 once each. explain your answer. Penny Nom lui répond. 





A ten digit number 
20071111 

jeff pose la question : find the greatest tendigit positive multiple of 12 using each digit once and only once Penny Nom lui répond. 





The sum of the digits of a whole number is 200 
20071106 

Kristin pose la question : If te sum of the digits of a whole number is 200, the whole number may not have
________ digits? Penny Nom lui répond. 





Show that there is no fivedigit number which 
20071004 

Greg pose la question : show that there is no fivedigit number which uses each of the digits 1,2,3,4,5 such that the numbers formed
by the first digit is divisible by 1,
by the first two digits is divisible by 2
by the first three digits is divisible by 3,
by the first four digits is divisible by 4,
by the first five digits is divisible by 5 Stephen La Rocque, Claude Tradif and Victoria West lui répond. 





Finding the last nonzero digits of large factorials 
20071004 

Mukesh pose la question : i have to find last five non zero digits of integer which can be very large (
upto 10^12) . i can find last non zero digit of of any factorial. Now my problem is that
i have to find last five non zero digit of factorial and also i want to general method for
last K non zero digits of factorial n. For example 10!=3628800 so last non zero digit is 8 ,last two
non zero digit is 88 .....and last five non zero digit is 36288. Victoria West lui répond. 





Three digit numbers where all digits are even 
20070914 

Cielo pose la question : Hannah made a list of all of the three digit whole numbers where all three digit were even. How many three digit whole numbers were on Hannah's list? Penny Nom lui répond. 





A question about integers 
20070824 

Jerry pose la question : Does there exist a positive integer such that when it is written in base 10 and its leftmost digit is crossed out, the new number is 56 times less than the original number? Stephen La Rocque and Penny Nom lui répond. 





who am i? 
20070808 

Phillip pose la question : if you hold a mirror horizontally across my middle, i look the same in the mirror.if you hold a mirror between my second and third digits,i look the same in the mirror if you turn me upside down, i look the same. what 6 fourdigit numbers could i be? Penny Nom lui répond. 





The smallest 5digit even number 
20070626 

charles pose la question : Using the digits 0,1,2,3,4 and 5 only once give the smallest 5digit even number Penny Nom lui répond. 





All 4 digit combinations for numbers 0 through 9 
20070621 

Jessica pose la question : How can I find all 4 digit combinations for numbers 0 through 9? Penny Nom lui répond. 





A 5 digit key 
20070531 

Michael pose la question : I have a 5 digit key pad lock on my truck.
I want to print out all of the combinations to try.
pad one=0 pad two =1 pad three=2 pad four=3 pad five =4.
can you help me find and print all combinations? Harley Weston lui répond. 





How many ways can I choose 4 numbers from 10? 
20070510 

Mitch pose la question : Can you give me a list of all possible four digit combinations using 0 to 9 no repeat numbers and the numbers do not have to be entered in a special order. If you could also show me how to calulate this it would be great Stephen La Rocque lui répond. 





Seven digit account numbers 
20070309 

Miranda pose la question : Account numbers for the Central Oil Company consist of seven digits. If the first digit cannot be 0, how many account numbers are possible? Thank you so much!!! Penny Nom lui répond. 





Four digit numbers 
20070226 

Anton pose la question : Hello! I would like to ask you how many combinations are possible using 4 digit number. # # # # (1...9).There is no zero,numbers don't repeat,second and forth are odd.Thanks Penny Nom lui répond. 





A twodigit number is five times its units digit. 
20070221 

Pamela pose la question : A twodigit number is five times its units digit. If the digits are reversed, the resulting number is 27 more than the original number. Find the original number. Gabriel Potter and Penny Nom lui répond. 





*** x ** = **** 
20070216 

Dani pose la question : Use the numbers 19 only once to make the following: A three digit number times a two digit number that gives a four digit number. That is *** x ** = **** (the numbers 19 can only be used once for each star). I came up with the answer 138 x 42 = 5796 but I want to know whether this is the only solution and if not, is there a formula to come up with the answer. Thanks! I appreciate your help! Chris Fisher and Claude Tardif lui répond. 





The sum of the digits of a twodigit number is 13. 
20070127 

Liz pose la question : The sum of the digits of a twodigit number is 13. If the digits are reversed, the new number is 9 more than the original number. Find the original number. Penny Nom lui répond. 





2 digit combinations 
20061204 

Gary pose la question : please figure out for me what are the 2 digit combinations of numbers using numbers 0 thru 9 Penny Nom lui répond. 





My greatest digit is 9, ... 
20061117 

Tiffany pose la question : My greatest digit is a 9, but less than 900. I'm one more than a multiple of 10 and the sum of my digits is 12. Who am I? Penny Nom lui répond. 





How can half of 12 be 7? 
20061116 

Liz pose la question : How can half of 12 be 7? Steve La Rocque, Chris Fisher and Penny Nom lui répond. 





What is the highest number possible with 3 digits? 
20061116 

Liz pose la question : What is the highest number possible with 3 digits? The teacher said the answer is not 999 and that the question did not say "3digit number." My answer then is 9 to the 99th power (written mathematically of course) as this uses "3 digits" and is obviously a huge number. Is this correct? Stephen La Rocque lui répond. 





Four digit combinations 
20061026 

Sasha pose la question : CAN YOU LIST ALL OF THE POSSIBLE 4 DIGIT COMBINATION'S, THAT DO NOT START WITH 0? Stephen La Rocque lui répond. 





Write the digits 1 to 9 on index cards, ... 
20061019 

Kim pose la question : Write the digits 1 to 9 on index cards, arrange the cards to form three 3digit numbers (using each card only ONCE). The third number is the sum of the first two numbers ** how many different ways can you do this?? ** Penny Nom lui répond. 





What number could it be? 
20060927 

Jonathan pose la question : What number could it be?
It is between 12000 and 13000
Its hundreds, ten and ones digits are all odd
the sum of all its digits is 12. Steve La Rocque and Claude Tardif lui répond. 





A threedigit number multiplied by 7, then 11, then 13 
20060917 

Sherrie pose la question : why is it true that a threedigit number multiplied by 7, then 11, then 13 will result in the three digits repeated twice? Stephen La Rocque lui répond. 





How many different threedigit numbers can you make using ... 
20060912 

Beth pose la question : How many different threedigit numbers can you make using the numbers 2, 5, 7, 8 using the digits any number of times? Stephen La Rocque and Penny Nom lui répond. 





Two characters 
20060912 

Robert pose la question : I am looking to find out how many possible unique combinations I can have if at any time i can use only two characters of numbers or the alphabet...For ex., i can have 199 or i can have a1, a2, z1, z2 ... or i can have aa, ab, ac... i came up with possible combinations of 1295 or so... can you help? Penny lui répond. 





The last two digits 
20060722 

Sam pose la question : You have answered this question already but you only answered to one digit.
What are the last TWO digits of:
3 to the power of 1994
7 to the power of 1994
3 to the power of 1994 + 7 to the power of 1994
7 to the power of 1994  3 to the power of 1994
Paul Betts and Penny Nom lui répond. 





The last digit of a sixdigit number is 2. 
20060709 

GG pose la question : The last digit of a sixdigit number is 2. If the 2 is moved to the start of the number, the new sixdigit number is only a third of the original number. Find the original number.
Paul Betts, Chris Fisher, Penny Nom lui répond. 





How many digits are in the number 2^64? 
20060614 

Trang pose la question : How many digits are in the number 2^{64}? Stephen La Rocque lui répond. 





We are 2 pairs of consecutive 2 digit numbers ... 
20060513 

A perent pose la question : We are 2 pairs of consecutive 2 digit numbers that are factors of the number of feet in a mile. Who are we? Claude Tardif lui répond. 





10^100 in binary form 
20060510 

Headmaster pose la question : How many digits has the number 10^{100} if we write it in binary form? Chris Fisher, Paul Betts and Steve La Rocque lui répond. 





8digits numbers with their digits in decreasing order 
20060509 

Headmaster pose la question : How many 8digits number are there with their digits in decreasing order Penny Nom lui répond. 





A number theory problem 
20060505 

DeHayward pose la question : Find the 6digit number in which the first digit is one less than the second, the third is half of the second, the fourth is 3 times the third, and the last 2 digits are the sum of the fourth and fifth. The sum of all the digits is 24. Paul Betts lui répond. 





The sum of a three digit number and its three individual digits is 429 
20060408 

Megan pose la question : Gill has recently moved to a new house, which has a three digit number. the sum of this number and its three individual digits is 429. What is the product of the three digits which make up the house number? Chris Fisher lui répond. 





Four digit numbers 
20060325 

Kenvin pose la question : i was wondering how many possibilities is there for a four digit number with the same first two numbers and the last two is not one of the first with numbers 19 Stephen La Rocque lui répond. 





Five digit numbers 
20060325 

Tony pose la question : Can someone tell me how many unique five digit numbers can be generated using 09? Stephen La Rocque and Penny Nom lui répond. 





The first six million digits of PI 
20060308 

Lori pose la question : How many threes are there in the first six million digits of PI? Also how many nines? Stephen La Rocque lui répond. 





A nine digit number 
20060306 

Ryan pose la question : What is the total number of possible combinations of a nine digit number (ie., social security number) including repeating numbers? Stephen La Rocque and Penny Nom lui répond. 





Counting digits 
20060130 

Cynthia pose la question : I would like to know the easiest way to calculate the
total numbers of digits used by a printer to number the pages of a book from 1 to 250. Penny Nom lui répond. 





The number of combinations of the digits 0235588 
20051207 

Blake pose la question : If you have the digits 0235588 how many different combinations can you possibly form with these seven digits? Penny lui répond. 





Fill in the blanks 
20051205 

Bonnie pose la question : Distribute the numbers 1 through 9 on the lines below so that two equations are true.
_ _ x _ = _ _
_ x _ = _ _
Use each digit only once Penny Nom lui répond. 





Add one 1 at the beginning and at the end of a number 
20051113 

Samuel pose la question : If we add one 1 at the beginning and at the end of a number, this number is increased by 14789.
What is the sum of the digits of the number? Penny Nom lui répond. 





5 digit numbers that include 5 and exclude 8 
20051104 

Paul pose la question : figure out
how many 5 digit numbers are there that include the digit 5 and exclude the
digit 8.
show me how to do get to the answer. (23816) Paul Betts lui répond. 





Four digit numbers 
20051009 

David pose la question : I had a discussion with my father about how many four digit numbers you can make with 09. He was saying that there is 12,000 and that seems quite high for me. But can you tell me how many there are, and what exactly are they? Penny Nom lui répond. 





Three digit numbers 
20051004 

Jordan pose la question : i need to know how many 3 digit numbers there are Penny Nom lui répond. 





What is my number? 
20050916 

Bob pose la question : I have 6 digits.
100,000th digit is one less than my ones digit, eight greater than my 1,000's digit, twice my tens digit and four times my 100s digit. My 10,000s digit is 0
What is my number? Penny Nom lui répond. 





What is the ones digit of 3 to the 79 power? 
20050914 

Candice pose la question : What is the ones digit of 3 to the 79 power? Penny Nom lui répond. 





Whats the value of the digit 7 in 756,809? 
20050914 

Anastasia pose la question : Whats the value of the digit 7 in 756,809? Penny Nom lui répond. 





The number of four digit combinations 
20050809 

Kevin pose la question : My 12 year old has asked me how to figure out the number of four digit combinations possible using 0 thru 9 without repeating a number? Penny lui répond. 





A two digit number 
20050809 

Grace pose la question : I am a 2 digit number. Both of my digits are even. My tens digit is 8 more than my ones digit. What number am I? Penny Nom lui répond. 





The sum of the digits of 2^100 
20050611 

Richard pose la question : The sum of the digits was calculated for the number 2100, then the sum of the digits was calculated for the resulting number and so on, until a single digit is left. Penny Nom lui répond. 





How many digits? 
20050607 

Floren pose la question : The numbers 2^{1989} and 5^{1989} are written one after another. How many digits in all are there? Claude Tardif lui répond. 





A six digit answer 
20050518 

Angela pose la question : I have a 6 digit answer that is comprised of only 4 symbols: a square, a circle, a triangle, and an X. How many possible solutions are there and how is the best way to find out what ALL the solutions are? Penny Nom lui répond. 





Some four digit numbers 
20050416 

Lori pose la question : can u give me every possible combination of four numbers starting with the number three Penny Nom lui répond. 





The sum of the digits 
20050316 

kelsey pose la question : What is the sum of the digits in the decimal form of 2^{1999} * 5^{2002}? Claude Tardif lui répond. 





How many three digit numbers can I make from the four cards 
20050312 

Sue pose la question : I have four playing cards 2,3,4,5 of hearts. How many three digit numbers can I make from the four cards. Penny Nom lui répond. 





Six digit numbers with at least one 7 
20041227 

Behzad pose la question : How many sixdigit numbers contain at least one 7 in their decimal expansion? Penny Nom lui répond. 





Strings of 4 digits from 1,2,...,7 
20041209 

Tom pose la question : How many different combinations can be made of the numbers 17 in 4 string combinations in any order? EX:7235, 3517, etc...
And if you were to include the same 2 numbers in every combination, how many would that make? EX: Using 1 & 2: 1274, 5142, 2751, etc... Penny Nom lui répond. 





A five digit number 
20041006 

A parent pose la question : What is the 5 digit number in which the first 2 digits are the square of the 3rd digit and the last 2 digits are the square of the digit that is one less than the third digit? The sum of all the digits is 22. Penny Nom lui répond. 





A palindrome question 
20040928 

Lilly pose la question : 12, 21, 13, and 31 are the only doubledigit numbers whose squares are the palindromes of the squares of the palindromes of doubledigit numbers. I was wondering why it works for these numbers, and if only these numbers work this way. Chris Fisher and Penny Nom lui répond. 





Four and five digit numbers 
20040921 

Josy pose la question :
The question I have now in front of me is....Is a 4digit number always less than a 5digit number?
Hi Josy,
The digits in order are 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9. Thus the largest four digit number is 9999. The smallet 5 digit number is 10000.
Penny
Go to Math Central
Penny Nom lui répond. 





Some numbers less than 100 
20040917 

Paul pose la question : for how many numbers less than 100 is the digit in the ones place half the digit in the tens place? Penny Nom lui répond. 





The bar over repeating digits. 
20040907 

Debbie pose la question : I would like to know the name given to the bar that is written over the repeating digits of a decimal. Penny Nom lui répond. 





Four digits 
20040710 

Rob pose la question : I am always interested to know how the for digit works. I mean, you have correctly put it that the total numbers obtain from 0000 thru 9999 are 10,000. My question is, is there any simple formula to turn this simple 4 figures of say: 1234. Penny Nom lui répond. 





Jack's social security number 
20040608 

A student pose la question : Jack's social security number contains each of the nonzero digits exactly once. By examining the digits from left to right, he also found that 1 divides the first digit evenly, 2 divides the sum of the first two digirs evenly, 3 divides the sum of the first three digits evenly, and so on, until 9 divides the sum of all the digits evenly. What is Jack's social security number? Penny Nom lui répond. 





A 3 digit number divisible by 7 
20040503 

A student pose la question : We need to arrange 1,3 and 6 to form a 3 digit number that is divisible by 7. Penny Nom lui répond. 





Digits in the decimal expansion 
20040211 

Leslie pose la question : In the decimal expansion of 1/17 what digit is in the 1997th place? Penny Nom lui répond. 





The digits in 349 
20030912 

Franik pose la question : in the number 349, which number has the least value, and why? Penny Nom lui répond. 





7,473,000,000 divided by 52000 
20030906 

A student pose la question : I am having trouble with a question. 7,473,000,000 divided by 52000. Our calculater gets 147311.5385. I come up with 143711.53846, and then the number starts to repeat itself Penny Nom lui répond. 





Four digit combinations 
20030904 

Emma pose la question : I seriously need to find out all the four digit combinations from 0 to 9!!! My name Is Emma Dibitt and I'm going into 8th grade and I'm a student!!! Penny Nom lui répond. 





The units digit of 57 to the 28th power 
20030901 

Maria pose la question :
If 57 is raised to the 28th power, what must be the units digit in the result? If you raise 7 to the 500th power, what is the numeral that will appear in the units digit position? Penny Nom lui répond. 





39 consecutive natural numbers 
20030819 

A student pose la question : Prove that among any 39 consecutive natural numbers it is always possible to find one whose sum of digits is divisible by 11. Penny Nom lui répond. 





Inserting a comma ever three digits 
20030725 

Linda pose la question : when writing a large number, why do we insert a comma every three numbers instead of every two or four numbers? Penny Nom lui répond. 





Four digit palindromes 
20030505 

Heather pose la question : How many palindromes were in between the numbers 1000 and 9999? Penny Nom lui répond. 





Three digit number 
20030310 

Grace pose la question : What three digit positive integer is exactly 32 times the sum of its digits? Claude Tardif lui répond. 





Combinations of 1,2,3,4,5 and 6 
20030201 

Kyle pose la question : Today I was aked a question by my geometry teacher. It was, what is the sum of all the possible combinations of the numbers 1, 2, 3, 4, 5, and 6. He said all the possible combinations were 720. I would like to know how u could do this, and what the answer is. Penny Nom lui répond. 





6 digit numbers from 0,0,2,2,4,4 
20030123 

Amanda pose la question : How many 6 digit numbers can you make from the numbers 0,0,2,2,4,4, giving that 0 cannot come first. The number has to contain 2 twos, 2 fours, and 2 zeros. Penny Nom and Claude Tardif lui répond. 





4 x abcd = dcba 
20021120 

A student pose la question : Say you have a four digit number (e.g. abcd) and you multiply the number by 4. The answer you get will be the reverse order of the number you started with (dcba). What is the number? The four digits (a,b,c,d) cannot be the same number or cannot be repeated. Penny Nom and Claude Tardif lui répond. 





Rounding 27.27 
20021103 

A parent pose la question : If you have a problem 27.27 and you need to round to the first 7 the answer would be 27 Would 27.0 be acceptable as well or is it completely wrong. Penny Nom lui répond. 





What are the digits? 
20021024 

Ebenezer pose la question : There are three digits. The middle digit is zero and the sum of the first and last digits are is 13. When the number is reversed it is increased by 297. What are the digits? Penny Nom lui répond. 





Use each digit 19 only one time each,... 
20021019 

Megan pose la question : Use each digit 19 only one time each, divide the numbers into 3 groups, make one 2 digit number, one 3 digit number, and one 4 digit number. There are 6 combinations of these numbers in which you can multiply the 2 digit and 3 digit number together to get the 4 digit number (using each digit 19 one time each). What are they!!!!!!!!!???????????? Claude Tardif lui répond. 





I am a 3 digit number. 
20020906 

Jasmine pose la question : I am a 3 digit number. My last digit is 3 times my first digit. My firat digit is twice my middle digit. What numbers am I? There are at least 2 correct answers? Paul Betts lui répond. 





Counting 
20020621 

Rachel pose la question : How many different numbers of 2 different digits each can be formed using the digits (1,3,5,7,9)?
How many triangles are formed by the vertical of a regular hexagon? Penny Nom lui répond. 





Numbering pages 
20011115 

Lucy pose la question : A printer uses 1008 digits to number the pages of a book. How many pages are there in the book? Penny Nom lui répond. 





The 100 chart 
20010928 

Nich pose la question : Am I suppose to use the 100 chart for these questions. Question One: I am a 2 digit number my tens digit is 2 more than my one digit my 1 digit is between 4 & 6. What # am I ? Question Two: I am a 2 digit # I am greater than 40 but less than 60 my tens and ones digits are the same I am a odd number what am I ? Penny Nom lui répond. 





I have 6 digits. 
20010906 

Kristan pose la question : I have 6 digits. My hundred thousands is 1 less than my 1 digit, 8 greater than my thousands digit, twice my tens digit, and 4 times my hundreds digit. My ten thousands digit is 0. What # am I? Penny Nom lui répond. 





How many 6 digit numeral combinations 
20010426 

Bryan pose la question : How many 6 digit numeral combinations are there If you can only use 6 digits (1, 2, 3, 4, 5, 6) and no number can be used twice in the Numeral! Claude Tardif lui répond. 





The number of occurrences of 0 is __, of 1 is __, of... 
20010417 

Martyanne pose la question : "In this sentence the number of occurrences of 0 is __, of 1 is __, of 2 is __, of 3 is __, of 4 is __, of 5 is __, of 6 is __, if 7 is __, of 8 is __, of 9 is __."
Each blank is to be filled with a numeral of one or more digits, written in decimal notation. Claude Tardif lui répond. 





The repetend in repeating decimals 
20010321 

Sharon pose la question : What is the name for the bar over the repetend in repeating decimals? Also, what is the name of the long division "house"? Penny Nom lui répond. 





The sum of all tendigit numbers. 
20010110 

John pose la question : Compute the sum of all tendigit numbers. Can you determine the sum of all n digit numbers? Sukanta Pati lui répond. 





Divisibility by 16 
20001212 

Shiling pose la question : A number can be divided by 16 if and only if its 1st four digits can be divided by 16. How can you prove that? Penny Nom lui répond. 





Six digit numbers using 1,2,5,6,7, and 9 
20000320 

Rachel pose la question : How many different sixdigit numbers can you make using the digits 1,2,5,6,7, and 9? How many of these six digit numbers are divisible by six? Claude Tardif and Denis Hanson lui répond. 





Bases other than 10 
19991206 

Garret Magin pose la question : We are doing a lesson on numbers of other bases than 10. We are working with binary, octal, and Hexadecimal. I was wondering what is used to represent number of different bases other then 16? Does it just continue on with the alphabet and if so what happens when you get to Z. It would be a help if you could answer this because it is really bugging me. And none of the math teachers at my school could let me know. Claude Tardif and Patrick Maidorn lui répond. 





Numbers with the digit 2 in 1...1000 
19990920 

Jessica pose la question : Is there a trick to finding out how many numbers containing the digit two is there from 1 to 1000? Walter Whiteley lui répond. 





A Puzzle 
19981027 

Bruce Bragnu pose la question : We are trying to solve what SHOULD BE a simple 7th grade problem and have run into a wall. It is: ABCD ABCD ABCD ABCD  EBEA It is an addition problem. Each particular letter represents the same digit. We are looking for what number "B" represents. We have tried a multitude of solutions and have come up empty. Penny Nom lui répond. 





Social Security Numbers 
19980707 

Valerie Lucas pose la question : How many social security numbers are possible? the answer is 10^9 why isn't the answer 9^9? Harley Weston lui répond. 





The twodigit numbers from 1099 
19980121 

Alexis Riddle pose la question : My name is Alexis. I'm a student in 8th grade and I'm taking Algebra I Honors. My question is: In a string of numbers, two adjacent digits are considered as a twodigit number. For instance, the string 11012 contains the numbers 10, 11, and 12. What is the number of digits in the smallest string that contains all of the twodigit numbers from 1099? Please help and thank you for any assistance you can give me. Penny Nom lui répond. 





Driving me CRAZY. 
19971117 

Billy Tran pose la question : Write a two digit number (both digits different and neither equal to zero) and then express the same number but now composed of the same two digits in reverse order with some mathematical symbol (+, , *, /, roots, !, or exponents). for example: 25 = 5^2. Now give me another. Hope you get this, cause its driving me CRAZY Penny Nom lui répond. 





How many digits are there in 2^2520? 
19961007 

Rita Leung pose la question : A)The number 64 is a sq., a cube, and a sixth power because 64=8*8, 4*4*4, 2*2*2*2*2*2. Find the smallest integer greater than 1 that is a sq., a cube, a 4th, 5th, 6th, 7th, 8th, 9th and 10th power. I have found that the answer is 2 to the power 2520th. B) How many digits are in the correct answer to part A? The answer is uncertain. It is either 758 or 759. Can you give me any ideas? Penny Nom lui répond. 





Repeating decimals 
19960909 

Alice pose la question : What is the line called that is placed over the decimal to show that it is infinitely repeating? The Centralizer lui répond. 

