A varies inversely with the square of r r and when r = 6 , A = 8 . Find r when A = 32

Question

Write a function describing the relationship of the given variables.

Answer 1

A = k/R^2

 

8 = k/6^2 = k/36

 

k = 8 * 36 = 288

 

A(r) = 288/r^2

 

32 = 288/r^2

 

32*r^2 = 288

 

r^2 = 288/32 = 9

 

r = +or- 3