Question

In a building there are 24 cylindrical pillars. The radius of each pillar is 28 cm and height is 4 m. Find the total cost of painting the curved surface area of all pillars at the rate of 8 per $m^2$ [2 MARKS]

Answer 1

Formula of a cylinder : 0.5 Marks
Concept; 0.5 Marks
Solution: 1 Mark

Radius of cylindrical pillar, r = 28 cm = 0.28 m

Height, h = 4 m

Curved surface area of a cylinder $=2\pi rh$

Curved surface area of a pillar $=2\times \frac{22}{7}\times 0.28\times 4=7.04m^2$

Curved surface area of 24 such pillar $=7.04\times 24=168.96m^2$

Cost of painting an area of $1m^2=Rs.8$

Therefore, cost of painting $1689.6m^2$
$=168.96\times 8=Rs.1351.68$