Question

$12$ cylindrical pillars of a building have to be cleaned.If the diameter of each pillar is $42$cm and the height of each pillar is $5$m, what will be the cost of cleaning these at the rate of Rs.$5$ per sq.m

Answer 1

Diameter of pillar$=42$cm

Radius$=r=\frac{42}{2}=21$cm$=\frac{21}{100}$m

Curved area of pillar$=2\pi rh=2\times \frac{22}{7}\times \frac{21}{100}\times 5=6.6$sq.m

Total area of $12$ pillars$=12\times 6.6$sq.m$=79.2$sq.m

Cost of cleaning for $1$ sq.m$=$Rs.$5$

Cost of cleaning for $79.2$ sq.m$=$Rs.$5\times 79.2=$Rs.$396$

$\therefore$ Cost of cleaning for $79.2$ sq.m$Rs.396$