Question

If the cost of painting the CSA of a cylinder of height 20 m at ₹ 40 per sq.m is ₹ 8800, then radius is .

• A. 1.75 m
• B. 7 m
• C. 3.5 m

Answer 1

The correct option is A 1.75 m

Cost of painting the CSA
= ₹ 8800
Cost of painting per square metre
= ₹ 40
Hence, CSA that was painted
$=\frac{8800}{40}=220m^2$
Given, height of cylinder $=20m$
$\because$ Curved surface area of cylinder $=2\pi rh$
$\Rightarrow 2\times \frac{22}{7}\times r\times 20=220$
$\Rightarrow r=\frac{220\times 7}{20\times 2\times 22}$
$\Rightarrow r=1.75m$
Hence, radius of the cylinder $=1.75m$