Question

A cylindrical pillar is $50$ cm in diameter and $3.5$ m in height. Find the cost of painting the curved surface of the pillar at the rate of $12.50$ per m${}^2$.

Answer 1

Given:

$H=3.5$ m, $R=\frac{50}{2}=25$ cm $=\frac{25}{100}=0.25$ m

$\Rightarrow$CSA$=2\pi rh=(2\times \frac{22}{7}\times 0.25\times 3.5)$ m${}^2$

$=5.5$ m${}^2$

$\Rightarrow$Cost of painting $1$ m${}^2$ area $=$ Rs.$12.50$

$\Rightarrow$Cost of painting $5.5$ m${}^2$ area

$=$ Rs.$5.5\times 12.50$

$=$ Rs.$68.75$