Suppose that w is direclty proportional to y and inversely proportional to v. If w=12 when v=20 and y=10, find w when v=30 and y=5.

Question

Basic Algebra

Directly Proportional and Inversely Proportional

Answer 1

Hi Sam,

 

If something is directly proportional, the formula is y = kx where k is some constant that you have to find.

If it is indirectly proportional, then the formula is y = k/x where k is again a constant.

Here you have three variables so your formula will be: w = ky/v

 

First you must solve for the constant k and so we substitute: 12 = k(10)/20 and solve for k to get 24.

 

Then you set up a second equation using the formula, now substituting k and get: w = 24(5)/30

so w=4.