







w varies jointly with the square of u and the cube of d 
20130126 

From Desiree: i don't understand how to answer this 'w varies jointly with the square of u and the cube of d' Answered by Penny Nom. 





Coefficient of variation 
20110414 

From Braden: When determining coefficient of variation (CV) or %CV is it possible to calculate %CV for two variables? For instance can %CV be used to determine the precision of 5 data points on a graph using the X and Y coordinates? or does %CV need to be determined for each variable separately? Answered by Robert Dawson. 





Proportionality 
20100227 

From Nazrul: If a is proportional to b then how can I prove that (a^2b^2) is proportional to ab. Please show me the process in details. Answered by ms. Dame and Tyler Wood. 





Proportionality 
20091103 

From Nazrul: If x is proportional to y , how can I prove that (x^2y^2) is proportional to xy.
Please explain the process. Answered by Penny Nom. 





Proportionality 
20090629 

From Nazrul: If x is proportional to y and y is proportional to z , how can I prove that (x^2+y^2)^3/2 is proportional to z^3 Answered by Harley Weston. 





Direct and inverse relationships 
20090406 

From allison: A piece of string is cut into n pieces of equal lengths L
(1) does n vary directly or inversely with L Answered by Penny Nom. 





Direct, inverse and indirect proportionality 
20090304 

From Brian: My 14 year old is confused about indirectly proportional and inversely proportional. On searching on the internet we were directed to:
http://mathcentral.uregina.ca/QQ/database/QQ.09.00/ellis1.html
Here leanne starts explaining indirectly proportional and ends up describing inversely proportional. Has Leanne got it wrong ?
What is indirectly proportional.
Thanks
Brian Answered by Chris Fisher. 





Coefficient of variation 
20081217 

From JR: I have read your reponses regarding the coeffcient of variation (CV) and find them very useful. I still have a question about interpreting the CV. Let's that the CV of sample #1 is 3% and that of sample #2 is 12%. Can I report that Sample #2 is 4 times more variable than sample #1? Thanks in advance! Answered by Robert Dawson. 





Partial variation 
20081103 

From Diamond: what are the 2 parts of partial variation? Answered by Penny Nom. 





Inverse variation 
20080522 

From leria: In Boyle's law, the pressure of gas varies inversely with the volume of the gas. A volume of 11.2 liters of air exerts a pressure of 2.0 atmospheres.
determine the constant of variation and write an equation the models the relationship between the pressure of the gas P and its volume, V. Use the equation to predict the volume of air necessary to exert a presure of 0.25 atmospheres. Answered by Janice Cotcher. 





Direct and inverse variations 
20071127 

From Julie: Please Help I do not understand this question. X varies directly as the square of S and inversely as T. How does X change when S is doubled ? When both S and T are doubled ? I appreciate your help with this problem. Answered by Stephen La Rocque. 





Variation 
20071029 

From deeqa: 1. A car traveled 175mi at a certain speed. If the speed had been 20mph faster,
the trip could have been made in 1hr less time. Find the speed
2. The average weekly allowance A of children varies directly as their grade level, G.
If the average allowance of an 8thgrade student is $8.56 per week, what is the average
weekly allowance of a 5thgrade
The time T required to do a job varies inversely as the number of people P working. It takes 2hr for 4
working. It takes 2 hrs for 4 volunteers to distribute flyers to a neighborhood. How long would it take 12
volunteers to complete the job? Answered by Penny Nom. 





Direct variation 
20071007 

From Kimberly: If y is directly proportional to the square of x,
and x=2 when y=12, then what is the value of y when x=3? Answered by Penny Nom. 





Direct variation 
20070507 

From Jennifer: assume that y varies directly as x. find y when x = 54 if y =1/4 when x=3/2 Answered by Stephen La Rocque. 





Direct and inverse Variation 
20070403 

From liz: how do you tell if an equation varies Directly or Inversely? ex.
x= 2y or
xy+12=3
i know that if you have three numbers (x. y, z) that it varies jointly but how do you tell if it is Inverse or Direct?
Thanks for the Help!
liz Answered by Stephen La Rocque. 





What is the intensity 5m below the surface? 
20070331 

From david: I have this question which I am supposed to set it up and solve as a differential equation. I know how to solve the diffrential equation but I am having hard time understanding this question. Here is the question: The intensity of light in the ocean decreases the deeper you dive. In fact, the rate at which the intensity decreases is proportional to the current intensity. Setup the corresponding differential equation and solve for I(Y), the intensity I as a function of current intensity Y. If the light intensity 2m below the surface is 25% of the intensity at the surface, what is the intensity 5m below the surface. Can you please explain to me what does it mean by current intensity and how do I set this equation up. Thanks for the help. Answered by Penny Nom. 





Direct and inverse variation 
20070303 

From Rene: Hi I'm Rene, I'm stuck with some problems in direct and inverse variation.
I know how to solve direct and inverse problems when only one variation is in a question at a time.
EX: p varies inversely as the square root of q, and when p=12, q=36 find p when q=16
12*6 =p*4 72=4p 18=p
But how would you solve a problem like.....
If s varies directly as r and inversely as t, and s=10 when r=5 and t=3, for what value of t will s=3 when r=4 ? Answered by Penny Nom. 





What is the diameter of the planet? 
20061207 

From Niall: In April 2005, scientists claimed to have captured light from an extrasolar planet orbiting a brown dwarf in the constellation Hydra some 230 lightyears from Earth. The scientists believe the planet is about five times the mass of Jupiter.
Assume the planet has the same density as Jupiter. What is the diameter of the planet? Answered by Stephen La Rocque. 





Direct variation 
20061105 

From Johann: The perimeter of regular octagon varies directly with the length of one side of the octagon Answered by Stephen La Rocque. 





Direct and Inverse variation 
20061027 

From Vishalinee:
i'm not sure how to use the words direct variation and inverse variation to describe thre relationship between: a. speed and distance b.speed and time c. distance and time. and then i need to create equations using the descriptions. i am really messed up with direct and inverse variation. Answered by Karen McIver. 





The coefficient of variation 
20060520 

From Glenn: What is the correct formula for coefficient of variation for a binomial distribution? Answered by Penny Nom. 





Coefficient of variation 
20051019 

From Jan: I am currently teaching the coefficient of variation and am wondering if there are some guidelines as to the interpretation of this statistic. I understand that it measures the variation in a variable relative to the mean  but what is the cut off for "too much" variation expressed in this way???
Answered by Andrei Volodin and Penny Nom. 





Direct and inverse variation 
20041005 

From Abraham: Given that y varies inversely as x and x varies directly as z.If z is doubled then y is halved.Why is that true.Please explain.I'm having trouble understanding the different types of variation Answered by Penny Nom. 





d varies inversely with g 
20040907 

From Ashlyn: d varies inversely with g when d=8 and g=2
a. write d as a function of g using function
notation.
b. find d(10). Answered by Penny Nom. 





A linear function 
20020909 

From Chad: If y = 9x  13 does it represent a linear function? And if it does what is its slope and is it a direct variation? Answered by Peny Nom. 





Ciefficient of variation 
20010923 

From Carmen: I have a question from my OAC finite class. I've come across a problem with the coefficient of variation. I have taught my students that there are no units for coefficient of variation and it can be expressed as a percent. So, for example, a set of data with mean of 5 and standard deviation of 100 would have a CV of 5%. But what happens in this situation: the mean is 4meters and the standard deviation is 0.7mm. Is the CV 1.75% or 0.00175% or 0.0175%? I've had some students change leave the units as is, change them both to mm or change them both to meters...so which is it and why? Answered by Penny Nom. 





Direct and inverse variation 
20001212 

From Ashley: I'm stuck on this unit of direct and inverse variation..please and my problems and show me how to do each PLEASE!!! Assume that y varies directly as x If y= 4 when x = 2, find y when x= 6 Assume that y varies inversely as x If y =4 when x=2, find y when x =6 Answered by Penny Nom. 

