Question

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

Answer 1

External diameter of cylinder $=1.4m$

$\therefore$ External radius = $\frac{1.4}{2}=0.7m$

or Radius of hemisphere = 0.7 m

Height of cylinder, h = 8 m

Total outer area to be painted = $2\pi rh+\pi r^2+2\pi r^2$

= $\pi r(2h+3r)$

= $\frac{22}{7}\times 0.7(2\times 8+3\times 0.7)$

= $2.2\times 18.1=38.82m^2$

Cost of painting = Rs. $(38.82\times 10)=Rs.388.2$