Direct and inverse proportions

Question

1. If y is inversely proportional to x² and y=5 when x=4, find the value of y when x=2.

2. If y is inversely proportional to r² +1 and y=32 when r=1, find the value of y when r=7

3. If u is inversely proportional to the square root of v and u=10 when v=9, find the value of a when v=22

Answer 1

y=k/x^2

5=k/16

k=80

y=80/4=20 when r=2

y=32/(f^2 +1)=32/50= 16/25=.64 when r=7

y=30/sqrv= 30/sqr22 when v=22