RRB Junior Engineer Stage 1 Model Papers 4

Here,
Radius of sphere $=\frac{17.5}{2}\mathit{c}\mathit{m}=8.75\mathit{c}\mathit{m}$
∴ Total surface Area of sphere $=4\mathit{\pi }{\mathit{r}}^2$
$=4\times \frac{22}{7}\times 8.75\times 8.75$
$=962.5\mathit{c}{\mathit{m}}^2$
After cut in two equal halves
∴ Total surface of both hemisphere $=2\times 3\mathit{\pi }{\mathit{r}}^2$
$\Rightarrow 2\times 3\times \frac{22}{7}\times 8.75\times 8.75$
$\Rightarrow 1443.75\mathit{c}{\mathit{m}}^2$
∴ Required increased area $=\left(1443.75\mathit{–}962.5\right)=481.25\mathit{c}{\mathit{m}}^2$