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 $\left(h\right)=3.5m$

Rate of painting the curved surface of the pillar $=\mathrm{Rs}.12.50\mathrm{per}{\mathrm{m}}^2$

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

STEP 1 : To Find the C.S.A of 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 2 : To Find the cost of painting curved surface of the pillar

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

Hence, 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 $Rs.68.75$.