Question

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

• A. 1.75 m
• B. 3.5 m
• C. 7 m
• D. 6 m

Answer 1

The correct option is A

1.75 m

Cost of painting the inner curved surface
= ₹ 8800
Cost of painting per square metre
= ₹ 40

Hence, area that was painted
= $\frac{8800}{40}=220m^2$


Thus, inner curved surface area
$=220m^2$

Inner curved surface area of cylinder
$=2\pi rh$

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.