Expert: Sherry Wallin - 2/4/2011

Question
A varies jointly as R1 and R2 and inversely as the square of L. Determine a when R1=120, R2=8, L=5 and k=3/2

Answer
Meisha~

The first variable mentioned that varies is always the dependent variable, that is by itself on one side of a variation problem so A is on the left hand side. To vary jointly means that you will have k times the product of the members that are jointly so in this case kR1R2 and finally when A varies inversely this means you have a constant k in the numerator and L^2 in the denominator:
A = k*R1*R2/L^2

So your job is to find A since you are given R1,R2, L, k:

A = (3/2)(120)(8)/5^2
= 1440/25
= 288/5

Math Prof