Question

$V=\pi (R^2-r^2)h$ ; make 'r' the subject of formula.

• A. $r=\sqrt{R^2+\frac{V}{\pi h}}$
• B. $r=\sqrt{R-\frac{V}{\pi h}}$
• C. $r=\sqrt{R^2-\frac{V}{\pi h}}$
• D. $r=\sqrt{R^2-\frac{V}{\pi h^2}}$

Answer 1

Answer: (C)

$r=\sqrt{R^2-\frac{V}{\pi h}}$

Given,
$V=\pi (R^2-r^2)h$

$\Rightarrow \frac{V}{\pi h}=(R^2-r^2)$

$\Rightarrow r^2=R^2-\frac{V}{\pi h}$

$\Rightarrow r=\sqrt{R^2-\frac{V}{\pi h}}$