Question

The diameter of a roller is $140$cm and $84$cm long.It takes $350$ complete revolution to level playground, determine the cost of levelling at the rate of Rs.$5$ per square metre.

Answer 1

Diameter$=140$cm

radius$=r=\frac{140}{2}=70$cm

Height$=h=84$cm

Curved surface area$=2\pi rh=2\times \frac{22}{7}\times 70\times 84=36960$sq.cm

Area covered in $1$ revolution$=36960$sq.cm

Area covered in $350$ revolution$=36960\times 350$

$=12936000$sq.cm

$=\frac{12936000}{100\times 100}=1293.6$sq.m

Cost of levelling $1293.6$sq.m$=1293.6\times 5=$Rs.$6468$