Question

Find the area to be painted in the following block with a cylindrical hole. Given that length is 15cm, width 12cm, height 20cm and radius of the hole 2.8cm.

Answer 1

Length of the given figure = 15 cm
Width of the given figure = 12 cm
Height of the given figure = 20 cm
Radius of the hole = 2.8 cm
$\therefore$ The area to be painted = Surface area of the figure - 2 $\times$ Area of the circular hole
$=2(lb+bh+lh)-2\pi r^2=2(15\times 12+12\times 20+15\times 20)-2\times \frac{22}{7}\times 2.8\times 2.8=2(180+240+300)-\frac{44\times 2.8\times 2.8}{7}=2\times 720-49.28=1440-49.28=1390.72c{m}^2$