Question

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

Answer 1

Number of pillars = 20

Diameter of one pillar = 0.50

$\therefore$ Radius (r) = $\frac{0.50}{2}$= 0.25 m

and height = 4 m

Curved surface area of one pillar =$2\pi rh=2\times \frac{22}{7}\times \frac{25}{100}\times 4m^2=\frac{44}{7}{m}^2$

$\therefore$ Total area of 20 pillars = $\frac{44}{7}\times 20=\frac{880}{7}{m}^2$

Rate of cleaning them = Rs. 2.50 per $m^2$

$\therefore$ Total cost = Rs. 2.50 $\times \frac{880}{7}$

=$Rs.\frac{250\times 880}{100\times 7}=Rs.\frac{2200}{7}$ = Rs. 314.28