







The square root of a large number 
20100119 

darlene pose la question : I understand the simple process, like 12 is the root to 144 but what happens when the number is 42563. Without a calculator how does a person figure this out during a timed test? Robert Dawson lui répond. 





The product of two numbers is 2400 
20081016 

belinda pose la question : The product of two numbers is 2400, one number is 20 more than the other number. what are the two numbers? Penny Nom lui répond. 





Compatible numbers 
20080925 

Katie pose la question : I am having trouble remembering how to find compatible numbers used to find the estimate in the foloowing problem. Can you please help me solve it and explain it to me? My son is in 5th grade and I need help. Thank you. Here is the problem: 2,752 / 28 estimate: 90 Penny Nom lui répond. 





The cube root of a really big number 
20080717 

Pete pose la question : Is the only way to find a cube root of a really big number guess and check, as i read in other questions, or is there another way without a calculator? Harley Weston lui répond. 





Estimate the cube root of 270 
20080311 

Tom pose la question : (a) By plotting suitable graphs, estimate to one decimal place the cube root of 270.
(b) With reference to your answer to part (a), use 8 iterations of a Bisection Search to refine your estimate. Use the nearest whole numbers either side of your estimate from part (a) as starting values.
(c) Using either of your starting values from part (b) as first guess, use the NewtonRaphson method to find the true value of the root (to 6 decimal places). Repeat using the other starting value from part (b) and compare the two results. Harley Weston lui répond. 





The irrationality of PI 
20070807 

Matthew pose la question : I have what I like to think of as a rather interesting question that I can't explain confidently for the life of me.
If we take a circle with a radius of 1 and we calculate the circumference, we can use 2 pi R.
Doing this calculation results in a circumference of 6.28318530717~ which goes on forever.
However, if you were to take a that same circle in the real world, say with radius 1cm and wrap a string around
it, and then measure the string, you don't get 6.28~, you get something like 6.2, a much more finite distance. The length
of the string is not an irrational number, like the math claims it to be. Claude Tardiff and Stephen La Rocque lui répond. 





Fill in the blanks 
20061004 

Justin pose la question : 1. To find out about how much, you can
2. The  states that the sum is the same no matter who you group the addends. Stephen La Rocque 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. 





50^99 and 99! 
20050523 

Romel pose la question : Which number is greater, 50^{99} or 99! Claude Tardif lui répond. 





How do you estimate the equation of a parabola? 
20021201 

Audrey pose la question : How do you estimate the equation of a parabola? I have a project where a must find parabolas in magazines and then estimate their equation. Penny Nom lui répond. 





x^{ 4} + x^{ 5} = 100 
20021027 

Bill pose la question : One of my students has stumped me. He asked how to solve the equation 4^{ x} + 5^{ x} = 100 All I can think of are graphing methods to get an approximate solution. What am I missing? Harley Weston lui répond. 





Dan is 4 inches taller than Mike. 
20020904 

A parent pose la question : Dan is 4 inches taller than Mike. Together they are 8 feet 8 inches tall. How tall is each boy in feet and inches. Penny Nom lui répond. 





A sample size problem 
20011028 

Charles pose la question : The U.S Transportation Dept. will randomly sample traffic reports to estimate the proportion of accidents involving people over the age of 70. The Dept. has no advance estimate of this proportion. how many reports should the dept select to be atleast 97% confident that the estimate is within .01 of the true proportion? Harley Weston lui répond. 





Linear regression 
20010801 

A student and a mother pose la question : My mom is taking a correspondence course in Simple Linear Regression and Correlation Analysis and we've been arguing about the relationship between the correlation rxy and standard estimate of errorSy.x. I took statistics last year in high school and I remember something about the Sy.x being proportionate to the r. Are they inversely related, directly related, not related, or can only range from 0 to 1.00? Her book doesn't say very much and I believe they are inversely related. She says they're directly related. Chris Fisher and Penny Nom lui répond. 





A confidence interval 
20010426 

Kim pose la question : A poll asked 1528 adults if they were in favor of the death penalty, 1238 said yes, find 99% confidence level for percent of all adult who are in favor of the death penalty. Andrei Volodin lui répond. 





Estimating the time to complete a job 
20001203 

Jack Hook pose la question : I'm a contractor and need to estimate how much time it will take me to do a specific job. A previous job I did was 6,480.16 Square Feet and I was able to paint it in 31.5 hours. In estimating my next job, how many hours will it take me to paint 11,000 Sqare Feet. Penny Nom lui répond. 





Sample variance 
20000416 

Jonathan Freeman pose la question : I was just reading your article entitled "A Note on Standard Deviation" I'm now teaching a unit on s.d. and my students were wondering why one uses a denominator of n for a population and n1 for a sample. I saw in your article that this is because "[the quantity] tends to underestimate sigma... and other technical reasons." To which my students again asked... "Why?" Could you please elaborate a bit on the "other technical reasons" perhaps in terms a high school senior (or their teacher...) could understand? Harley Weston lui répond. 





Estimates 
20000411 

Sue Jordan pose la question : I am looking for examples of estimates for underestimating and overestimating. When would you do each one. For my child age 11 6th grade. Penny Nom lui répond. 





Area of an irregular shaped objects. 
19990407 

Jesse Townsend pose la question : How do I find the surface area of an irregulary shaped object such as someone's knee from the thigh to shin? Thanks. Walter Whiteley lui répond. 





The bricklayers formula 
19981124 

Rachel Kaplan pose la question : I have to do a report on the bricklayers formula N = 7LH. Can you give me any information on this. Harley Weston lui répond. 





A Monte Carlo Procedure 
19970423 

Donna Hall pose la question : A irregularly shaped object of unknown area A is located in the unit square 0<=x<=1. Consider a random point uniformly distributed over the square. Let X = 1 if the point lies inside the object and X = 0 otherwise. Show that E(X) = A. How could A be estimated from a sequence of n independent points uniformly distributed over the square? How would you use the central limit theorem to gauge the probable size of the error of the estimate. Harley Weston lui répond. 





Approximating pi. 
19961104 

Ben Dixon pose la question : How do you calculate Pi? Do you have to somehow combine the equation for a circle with the formula for the circumference? Chris Fisher lui répond. 





Approximating roots. 
19961104 

Ben Dixon pose la question : How do you calculate a square root? eg the square root of 2.There is obviously some sort of successive approximation type algorithm for doing it to however many decimal places is required, but what is the algorithm? Harley Weston lui répond. 

