Question

A cylindrical pillar is $50cm$ in diameter and $3.5m$ in height.

Find the cost of painting the curved surface of the pillar at the rate of$Rs.12.50per{m}^2$.

(Assume $\pi =22/7$)

Answer 1

Given,

Diameter of cylindrical pillar $\left(d\right)=50cm=0.5m$

Height of cylindrical pillar $\left(h\right)=3.5m$

To Find out

We have to find the cost of painting the curved surface of the pillar at the rate of $Rs.12.50per{m}^2$

Solution:

Step 1 : To find the radius of the cylindrical pillar

The radius$\left(r\right)=\frac{d}{2}=\frac{0.50}{2}=0.25m$

Step 2 : To find the C.S.A of the cylindrical pillar

Curved surface area of cylindrical pillar

$$\begin{gathered} =2\pi rh \\ =2\times \frac{22}{7}\times 0.25\times 3.5 \\ =5.50m^2 \end{gathered}$$

Step 3 : To find the cost of painting the cylindrical pillar

Rate of painting $=Rs.12.50per{m}^2$

Cost of painting the curved surface of the pillar$=5.50\times 12.50=₹68.75$

Hence, the cost of painting the curved surface of the pillar at the rate of $Rs.12.50per{m}^2$ is $Rs.68.75$.