Question

X varies inversely as the square of Y. If X = 5 when Y = 2 , then find the constant of variation.

• A. 20
• B. 10
• C. 5
• D. 15

Answer 1

The correct option is A 20

Given, X varies inversely as the square of Y.
$\Rightarrow X\propto \frac{1}{Y^2}$
Let the constant of variation be k.
$\Rightarrow X=\frac{k}{Y^2}$
$\Rightarrow X{Y}^2=k$
Given, at X = 5, Y = 2.
So, $k=X{Y}^2=\left(5\right)\left(2^2\right)=20$.