Question

The diameter of a roller is $84$ cm and it's length is $120$ cm. It takes $500$ complete revolutions to roll once the play ground to level. Find the area of the play ground in $m^2$.

Answer 1

Roller is of the form cylinder

Radius $=\frac{Diameter}{2}=\frac{84}{2}=42$cm

Area of roller $=$ curved surface of cylinder

$=2\pi rh$

$=(2\cdot \frac{22}{7}\cdot 42\cdot 120)c{m}^2$

$=31680c{m}^2$

Area of $1$ revolution $=$ Area of roller $=31680c{m}^2$

Area of $500$ revolution $=500\times 31680c{m}^2$

Area of playground $=15840000c{m}^2$

$=15840000\times \frac{1}{100}\times \frac{1}{100}{m}^2$

$=1584m^2$.