Question

Total surface area of cylinder is $60\pi c{m}^2$ and its height $7cm$. Find the curved surface area of cylinder.

Answer 1

As we know that,

Total surface area of cylinder $=2\pi rh+2\pi r^2=60\pi {cm}^2\left(\text{Given}\right)$

Therefore,

$2\pi r^2+2\pi \cdot r\cdot 7=60\pi$

$r^2+7r=30$

$r^2+7r-30=0$

$r^2+10r-3r-20=0$

$(r+10)(r-3)=0$

$\because r\ne -ve$

$\therefore r=3cm$

Therefore,

Curved surface area of cylinder

$=2\pi rh=2\times \pi \times 3\times 7=42\pi {cm}^2$