Question

Twenty one cylindrical pillars of the Parliament House are to be cleaned. If the diametre of each pillar is 0.50m and height is 4m, What will be the cost of cleaning them at the rate of Rs. 2.50 per square metre?

Answer 1

Diameter of each pillar= 0.50m
$\therefore$ Radius (r) = $\frac{0.50}{2}=0.25m$
Height(h)=4m.
$\therefore$ Curved surface area of each pillar= $2\pi rh$
$=2\times \frac{22}{7}\times 0.25\times 4m^2$
$=2\times \frac{22}{7}\times \frac{25}{100}\times 4=\frac{44}{7}{m}^2$
$\therefore$ Surface area of 21 pillars $=\frac{44}{7}\times 21m^2$
$=44\times 3m^2$
$=132$
Cost of cleaning = Rs. 2.50 per $m^2$
$\therefore$ Total cost = Rs. $132\times 2.50$
= Rs. 330