Question

The diameter of a roller, $1m$ long, is $84cm.$ If it takes $500$ complete revolutions to level a playground, the area of the playground is

$\left(a\right)1440m^2\left(b\right)1320m^2\left(c\right)1260m^2\left(d\right)1550m^2$

Answer 1

The correct option is $\left(b\right):1320m^2$

Diameter of the roller $=84cm$

Radius, $r=42cm$

length, $h=1m=100cm$

Area of one revolution $=$ Curved Surface area of the cylindrical roller

$=2\pi rh=2\times \frac{22}{7}\times 42\times 100=26400c{m}^2$

Area of $500$ revolution $=26400\times 500=13200000c{m}^2=1320m^2$ [$\because 1m=100cm$]

Area of playground $=1320m^2$