Question

$x$ varies directly as $y^2$. Given that for $y=3,x=2$. What is the value of $x$ when $y=5$?

• A. $5\frac{5}{9}$
• B. $5\frac{4}{9}$
• C. $\frac{18}{25}$
• D. $\frac{12}{25}$

Answer 1

The correct option is A $5\frac{5}{9}$

$x$ is directly proportional to $y^2$

$x=k{y}^2$ where k is a constant

For $y=3,x=2$

$k=\frac{x}{y^2}=\frac{2}{3^2}=\frac{2}{9}$

For $y=5,x=k{y}^2=\frac{2}{9}\times 5^2=\frac{50}{9}=5\frac{5}{9}$