Question 7

# In a building there are 30 cylindrical pillars. The radius of each pillar is 35 cm and height is 5 m. Find out the cost of painting the curved surface of half the number of pillars. The rate of painting is Rs. 10 per $$m^2$$.

Solution

Curved surface area of cylindrical pillar is given as A = 2$$\pi$$rh, where 'r' is base radius and 'h' is height of the cylinder.

So curved surface area of each pillar A = $$2\times \pi\times 0.35\times 5 = 11 m^2$$

Given there are 30 cylindrical pillars.

The curved surface area of half the number of pillars = 15 * A = 165 $$m^2$$.

Given rate of painting is Rs. 10 per $$m^2$$

The cost of painting curved surface of half the number of pillars = Curved surface area * rate of painting

= $$165\times 10$$

= Rs. 1650.