Question

The cost of painting the inner curved surface area of a cylindrical container of depth 20 m is Rs. 8800. If painter takes Rs. 40 per metre square to paint the cylindrical container, then find radius of the cylindrical vessel.
Take $\pi =\frac{22}{7}$

Answer 1

Cost of painting the inner curved surface = Rs. 8800
Cost of painting per square metre = Rs. 40
Hence, area that was painted $=\frac{8800}{40}=220m^2$
$\Rightarrow$ inner curved surface area $=220m^2$

We know the inner curved surface area of cylinder = $2\pi rh$
Given: height of cylinder = 20 m

$\Rightarrow 2\times \frac{22}{7}\times r\times 20=220$
$\Rightarrow r=\frac{220\times 7}{20\times 2\times 22}$
$\Rightarrow r=1.75m$

Hence, radius of the cylinder = 1.75 m