Question

A rectangular strip $25cm\times 7cm$ is rotated about the longer side. Find the total surface area of the solid thus generated.

Answer 1

Dimensions of rectangular strip = $25cm\times 7cm$

By rotating the strip along longer side $\left(25cm\right)$, a solid (Cylindrical in shape) is formed whose

Radius $\left(r\right)=7cm$ and

Height $\left(h\right)=25cm$

$\therefore$ Total surface area of the solid generated (Cylindrical in shape) $=2\pi r(h+r)$

$=2\times \frac{22}{7}\times 7(25+7)c{m}^2$

$=44\times 32$

$=1408c{m}^2$