Question

x varies inversely as y^2, and x = 4 when y = 10. Find x when y = 2.

A. x = 16
B. x = 5
C. x = 80
D. x = 100

Answer 1

\[x=\frac{ k }{ y^2 }\rightarrow 4=\frac{ k }{ 10^2 }\rightarrow k=400\]\[x=\frac{ 400 }{ y^2 }\rightarrow x=\frac{ 400 }{ 2^2 }\rightarrow x=100\]

Answer 2

k is a proportionality constant