Question

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

Answer 1

Cost of painting the CSA
= ₹ 8800
Cost of painting per square metre
= ₹ 40
Hence, CSA that was painted
$=\frac{8800}{40}=220m^2$ $\left[1.5marks\right]$
\

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 $=1.75m$ (~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~[1.5~marks]\)