A cylindrical pillar has a diameter of 50 cm and a height of 3.5 m. What is the cost of painting its curved surface at the rate of Rs. 12.50 per m²?
Updated on May 13, 2025 | By Learnzy Academy
Diameter of the pillar = 50 cm = 0.5 m (since 1 m = 100 cm)
Then radius = Diameter ÷ 2 = 0.5 ÷ 2 = 0.25 m
Height of the pillar = 3.5 m
Rate of painting = Rs. 12.50 per m²
Step 1: Calculate the curved surface area (CSA) of the cylinder
The formula for the curved surface area of a cylinder is:
CSA = 2πrh
Where:
r = radius = 0.25 m
h = height = 3.5 m
Substitute the values:
CSA = 2 × (22/7) × 0.25 × 3.5
CSA = 2 × (22/7) × 0.875
CSA = (44/7) × 0.875
CSA = 5.5 m²
Step 2: Calculate the cost of painting
Cost = CSA × Rate
Cost = 5.5 × 12.50
Cost = Rs. 68.75
Hence the cost of painting the curved surface is Rs. 68.75
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