Question

A right circular cylinder just encloses a sphere (see figure). If the height of the cylinder is $21cm$, then find the surface area of cylinder (Take of $\pi =\frac{22}{7}$)

Answer 1

Given height of cylinder $=21$ $cm$

Let radius of circle is $r$

Cylinder encloses a sphere $⟹h=2r$

$⟹r=\frac{21}{2}$

Surface area of cylinder is $2\pi r(h+r)=2\times \frac{22}{7}\times 10.5\times 31.5$

$=2079$ $c{m}^2$