Question

A cubical box of side 2 m has a circular hole of radius 0.7 m on each of its four walls. Find the cost of painting the box at Rs. 10 per $m^2$.

Answer 1

Length of the side of the box (a) = 2 m

Hence, Total Surface Area of the box = $6a^2$

= $6\times 2^2$

= $24m^2$

Area of circular holes = Number of holes $\times$ Area of one circular hole = $4\times \pi r^2$

= $4\times \frac{22}{\text{/}7}\times \frac{\text{/}7}{10}\times \frac{7}{10}$

= $\frac{616}{100}=6.16m^2$

So, area to be painted

= 24 – 6.16

= $17.84m^2$

Hence, cost of painting = 10 $\times$ 17.84

= Rs. 178.4