. centre de ressources dilemmes et doutes le visage humain de mathématiques Qui sommes-nous Problème de mois activités de promotion babillard
Centrale des maths - centraledesmaths.uregina.ca
Dilemmes & doutes
« D & D »
. .
topic card  



liste de
. .
nouvelle recherche

50 articles trouvés pour ce sujet.
Significant digits 2017-08-06
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?


Penny Nom lui répond.
Canada's population as a percentage 2017-05-11
bethmarie pose la question :
What percentage of the world population (7.5 billion) is Canada's population (36 million). Thank you very much!
Penny Nom lui répond.
Shooting a ball at a target 2016-02-16
Thys pose la question :
I have a problem with the formula that i use .(for programming)
I have looked all over the web to find a solution but no luck.
I have a cannon that shoots a ball at a target
I use this formula to calculate what my initial velocity must be to hit the target at a angle of 30 degrees and a distance of 15m (the cannon and target position is known) It works perfectly if both is at same height but if one is higher or lower it miss.

In an example I am working with the range is 30m, the angle is 45 degrees and the target is 10m higher than my position.
Please help
Formula = V0 = √RG / Sin(2α)

Harley Weston lui répond.
Prove that you cannot factor x squared + 5 2015-05-28
lily pose la question :
the question is: prove that you cannot factor x squared + 5
Robert Dawson lui répond.
Percentage of water in a soil sample 2012-03-01
avi pose la question :
what i need is the formula in getting the percentage from gram. situation:
i need to know how many percent will i declare in getting the moisture of a soil sample i weighed 2,000 grams of soil before i dried it out in the oven, after few hours the recovery of the dried out soil is 1,700 grams. How many percent will be the water content? kindly send me a formula in computing this.
thank u very much!

Penny Nom lui répond.
Designing a tin can 2011-03-31
Tina pose la question :
A tin can is to have a given capacity. Find the ratio of the height to diameter if the amount of tin ( total surface area) is a minimum.
Penny Nom lui répond.
Multiplication and order 2011-01-21
Janet pose la question :
Robert Dawson lui répond.
[sec^2x]*[sec^2x] 2010-12-16
Hari pose la question :
Penny Nom lui répond.
How many zeros? 2010-03-18
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.
More on millions and billions 2010-03-11
julio pose la question :
shouldn't the thousands of millions, tens of thousands of millions, and hundreds of thousands of millions be called what they are? technically they are not billions because billions come after 999,999,999,999 . It would sound better to call the numbers by their real name when economists talk about the national deficit besides mathematics is a very precise science that doesn't admit mistakes. Or am I wrong? I know that in other countries is expressed different than here. I have this question to different people and nobody has a "logical" explanation to it. " that's the way is here in the US" does not explain any thing
Penny Nom lui répond.
A circle problem 2009-12-14
Fawad pose la question :
AP is a tangent at P to a circle centre O, where AP=6cm. The straight line AQC is such that QC= 9cm. Find the length, in cm of AQ.
Chris Fisher lui répond.
Divide and reduce to lowest terms. 2009-09-06
Karen pose la question :
Divide and reduce to lowest terms. Use the cancellation technique as needed 4 2/3 divided by 12 14/3 divided by 12/1 not sure wheer to go from here with the cancellation technique
Penny Nom lui répond.
Paddling downstream 2009-09-04
Nicole pose la question :
You head downstream on a river in a canoe. You can paddle at 6 km/h and the river is flowing at 2.4 km/h. How far downstream will you be in 55 minutes?
Penny Nom lui répond.
Fred in his canoe 2009-02-21
Susan pose la question :
Fred paddled for 4 hours with a 7 km/hr current to reach a campsite. The return trip against the same current took 9 hr. Find the speed of Fred's canoe in still water. (Remember to include correct units)
Penny Nom lui répond.
More on infinity and Set Theory 2009-02-17
Justin pose la question :
I greatly appreciate your help I was just wondering from your previous answer, why doesn't Cantor's cardinal numbers in set theory apply to the limit x->0, y=infinity?


Robert Dawson lui répond.
Infinity and Set Theory 2009-02-17
Justin pose la question :
I was just wondering is the limit x->0, y=1/x=infinity, the biggest uncountable infinity according to Cantor's cardinal numbers in set theory?


Robert Dawson lui répond.
Cantor's cardinality 2009-02-16
Justin pose la question :
Hello, I was just wondering why the infinity from real numbers is smaller than Beth Two in the context of Cantor's cardinality set theory?


Robert Dawson lui répond.
Why is the difference between british and american counting? 2008-12-15
Muhammad pose la question :
Why is the difference between british and american counting?
Example 1 Billion american = 1,000,000,000 but,
1 Billion British = 1,000,000,000,000

Robert Dawson and Harley Weston lui répond.
A wine decanter 2008-12-10
Suzanne pose la question :
I am trying to buy a wine decanter for my dad for Christmas. One big problem I am having shopping online is finding the right size. Wine is sold by metric ml, with a standard bottle holding 750ml of wine. Decanters are measured by oz, and the sizes are all over the place, with one site alone having sizes 25oz, 26 1/2oz, 50oz, 59 1/8oz, and 68oz.

Can you help me with metric conversions so I can figure out how much wine these decanters hold? Like everybody else, I need this as soon as possible so I can get it shipped in time for Christmas. (I'm disabled & don't drive, so online shopping is my only way to get gifts.)

Thanks for your help!


Chris Fisher and Robert Dawson lui répond.
A canal with cross section a semicircle 2008-10-19
Connor pose la question :
a canal with cross section a semicircle is 10m deep at the centre. Find an equation for the semicircle and use it to find the depth 4m from the edge
Penny Nom lui répond.
Distance, time and rate 2008-09-11
Pauline pose la question :
During the first part of a trip, a canoeist travels 100 miles at a certain speed. The canoeist travels 25 miles on the second part of the trip at a speed 5 mph slower. The total time for the trip is 5 hrs. What was the speed on each part of the trip?
Penny Nom lui répond.
Alpha level 2008-07-23
anonymous pose la question :
What is the advantage of using an alpha level of .01 versus a level of .05, What is the disadvantage of using a smaller alpha level?
Janice Cotcher lui répond.
Cantor's diagonal argument 2008-01-26
David pose la question :
Cantor's theory using a diagonal across a list of real numbers to proven uncoutability has always puzzled me.First in base ten, it feels like hocus pocus so I began thinking of the Boolean numbers as truer representations of place value (on,off). Secondly his list was always arbitrary or so I recollect. Therefore, I suggested using a seriesA=.10000....,B=.01000. C=.11000, etc. Any diagonal is already located among the numbers listed. My only alteration is that since the final digit is always unrepresentably either one or zero, but it must be one or the other, I make an assumption that if x= .abc...1 and y= .abc...2 the only two possibilities and I choose to count F=x+y then then the numbers are countable= Z=sumFi,where I=2+2^2+2^3...

I hope this sketch is enough description, I asked Rudy Rucker more formally but got no mathematical response, someone else gave me some tale about slippery epsilon. What do tyou think of recasting his proofs in more rigorous form? David French

Claude Tardif and Walter Whiteley lui répond.
What would be the cost of a 10 in * 15 in canvas? 2007-12-01
Jasmine pose la question :
a 40in *60 in canvas is sold for $60.00 if the price is determined by the cost of the material what would be the cost of a 10 in * 15 in canvas
Stephen La Rocque lui répond.
Countable and uncountable sets 2007-07-24
Mac pose la question :
Hi, i tried to read few webpages related to the countably infinite and uncountable sets. Even i read few questions from this forum.

But i am not convinced with this explanation. If you have any good book that explains this in layman term, please redirect me to that.
1) Can you please explain what is the difference between these too ?
2) How could you say set of Natural number and set of even numbers are countably infinite ?
N={1,2,3,...} and Even= {2,4,6,...}
When an element in the even set is some 2n, we will map it to 'n'.So now we have a bigger number(2n) right ?
Sorry, i didn't understand that.

Can you please help me out to understand that ?

Harley Weston lui répond.
A statistical difference 2007-07-03
a student pose la question :
I am writing a paper for a grad class in which I am comparing achievement levels of boys and girls. I have data that shows the average marks for girls and boys in each grade 12 subject for the entire province. My prof want me to show there is a statistical difference. What do I have to do to show this? I don't have access to the raw data, so don't know the SD. Is there anything I can do mathematically with the data that I have? (I can determine n for each set of data, it ranges between 2400 and about 13000 for each subject area.)
Chris Fisher and Harley Weston lui répond.
Surface area of a cylinder 2007-05-13
Nina pose la question :
if a cylinder is 23 ft high with a 12 ft radius, how do I find the surface area?
Penny Nom lui répond.
A point inside a circle 2007-05-04
edgemitter pose la question :
There is a point inside a circle (but not in its center) where two perpendicular secants intersect, dividing the circle into four regions with different area. Calculate the area of the four regions
Walter Whiteley lui répond.
What is the value of csc (-2pi/3)? 2006-06-04
Kishor pose la question :
What is the value of csc (-2pi/3)?
Stephen La Rocque lui répond.
A tangent to a parabola 2005-11-02
A student pose la question :
Find the point on the curve y=x2 where the tangent to the curve is parallel to the secant line connecting (-1,1) and (2,4)
Penny Nom lui répond.
Cubic feet and imperial gallons 2005-10-27
Dave pose la question :
What is the volume in cubic feet which is occupied by 1080 Canadian gallons of water?
Harley Weston lui répond.
Different infinities 2004-05-27
Plober pose la question :
How can I explain to a friend (in a bar, using as a pen and a paper napkin) that the integer's infinity is 'smaller' than the irrationals's one? The demo I tried was that you couldn't match the integers with the real numbers between 0 and 1 (that 0.xxxxx replacing the Nth number from a different one... that demo), but she used my argument >:| saying that you can add one to the integer's infinite, and the number I was creating was only one more...

I can't think of any other way, and I KNOW the real's cardinality is greater than the integer's one

Claude Tardif and Penny Nom lui répond.
Acres and square miles 2004-02-17
Richard pose la question :

How many acres are in .17 square miles? and How many acres are in .6 square miles?

The two areas I am requesting information about are Vatican City and San Marino, the two smallest countries in the world. If I can transfer the sq. miles into acres , I can relate the size of these countries to our school grounds and the students will better understand their sizes.

Penny Nom lui répond.
Multiplier and multiplicand 2003-12-17
Karen pose la question :
The K-5 curriculum states that at a grade 5 level students should "understand and use the terms multiplier, multiplicand" The curriculum defines 'multiplicand' as " a number being multiplied by another number. A factor." There is no definition given for 'multiplier' Question: Define these words- are they just other words for 'factors'. If so, how important is it that students use these terms? It would seem like 'factors' would be the better choice of words to use. If multiplcand refers to eg. the first factor in the equation and the 'multiplier' the seond term, (if in fact it does)- is this not confusing for students when we teach them that multiplication is commutative?
Penny Nom lui répond.
7,473,000,000 divided by 52000 2003-09-06
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.
Gallons in a tank 2003-03-20
Leslie pose la question :
I am trying to figure the liquid gallons in a water tank that is 19" wide by 29.25" long and is 12.25" high. Could you tell me the formula to figure this out.
Penny Nom lui répond.
Sasha's candies 2003-02-18
Pat pose la question :

Sasha and Trudy are playing tick-tac-toe. Sasha agrees to give trudy two pieces of candy for each game Sasha loses, and Trudy agrees to give Sasha three pieces of candy for each game that Trudy loses. After playing thirty games, Sasha has the amount of candy that he started with. If no ties occurred, how many games did Sasha win?

Paul Betts lui répond.
What is larger than infinity? 2003-01-12
Dana pose la question :
What is larger than infinity?
Claude Tardif and Harley Weston lui répond.
How many billions equal one trillion? 2002-12-07
Ryan and Aylah pose la question :
How many billions equal one trillion?
We believe that the answer is one thousand times one billion equals one trillion. Please help us with the answer to this question.

Penny Nom lui répond.
Radicals with fractional radicands 2002-11-11
A student pose la question :
how do I simplify radicals with fractional radicands?

ex. 7sqrt(2) + sqrt(50) - 2sqrt(18)

10sqrt(3/5) - 24sqrt(5/3)

3sqrt(2/9) + 1/2sqrt(32) + sqrt(9/8)

Penny Nom lui répond.
Rounding 27.27 2002-11-03
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.
For 7 the multiplicand is 143 2001-12-12
Cory pose la question :
For 7 the multiplicand is 143

I am asked to solve this, if you could help me it would be greatly appreciated!

Penny Nom lui répond.
Gallons 2001-11-19
Shawn pose la question :
Do we use British or American gallons in Canada?
Chris Fisher lui répond.
A trig identity 2001-07-27
Jeff pose la question :
prove this identity and show steps

Harley Weston lui répond.
A sugar cane crop 2001-03-27
A student pose la question :
a sugar cane farmer harvested only 1/4 of his crop. he sold 2/3 of his harvest to the mill. what fraction of the total crop did he sell.

darens recipe for florida fudge calls for 5/8 cup of sugar. if he wants to make only 1/2 of the recipe how much sugar should he use.

Penny Nom lui répond.
The path of a cannonball 2001-01-15
A student pose la question :
Artillerymen on a hillside are trying to hit a target behind a mountain on the other side of a river. Their cannon is at (x, y) = (3, 250) where x is in kilometers and y is in meters. The target is at (x, y) = (-2, 50). In order to avoid hitting the mountain on the other side of the river, the projectile from the cannon must go through the point (x, y) = (-1, 410).

Write the equation for the problem.

Penny Nom lui répond.
Minimizing the metal in a can 2000-05-02
May Thin Zar Han pose la question :
A can is to be made to hold 1 L of oil. Find the dimensions that will minimize the cost of the metal to manufacture the can.
Harley Weston lui répond.
Cross multiplication 2000-02-16
J E Swinton pose la question :
Why does cross multiplication work?

How come canceling work?

Penny Nom lui répond.
Two candles 1999-11-24
Skip Simpson pose la question :
You have two candles the same length. They are lit at the same time. One burns down in 4 hours; the other in 5 hours. How long does it take before one candle is three times the length of the other candle?
Walter Whiteley lui répond.
Cannonballs 1999-01-27
Roger King pose la question :
How many cannonballs can be stacked in a triangular pyramid?
Penny Nom lui répond.



Centrale des maths reçoit une aide financière de l’Université de Regina et de The Pacific Institute for the Mathematical Sciences.



accueil centre de ressources accueil Société mathématique du Canada l'Université de Regina PIMS