Question

A storage tank consists of a circular cylinder with a hemisphere adjoined on either end. If the external diameter of the cylinder be 1.4 m and its length be 8 m find the cost of painting it on the outside at the rate of Rs. 10 per $m^2$

Answer 1

Diameter of the tank = 1.4 m
$\therefore$ Radius $\left(r\right)=\frac{1.4}{2}m=0.7$
and height of cylindrical portion = 8 m

$\therefore$ Outer surface area of the tank
$=2\pi rh+2\pi r^2=2\pi r(h+r)=2\times \frac{22}{7}\times 0.7(8+0.7)m^2$
$=\frac{2\times 22\times 7}{7\times 10}\left(8.7\right)m^2=\frac{44}{10}\times 8.7$
Rate of painting = 10 per $m^2$
$\therefore Totalcost=Rs.\frac{44\times 8.7\times 10}{10}=Rs.382.80$