Question

The diameter of a roller is 84 cm and its length is 120 cm. It takes 500 complete revolutions to roll once over the play ground to level. Find the area of the play ground in sq.m

Answer 1

hope its right thanx

Answer 2

Answer:

GIVEN,

Diameter of a roller 2r = 84 cm,

Length ( height) h = 120 cm.

Since, roller is cylindrical, hence in one revolution it covers the area of the ground equals to its curved surface

$∴ \: \: curved \: surface \: = 2\pi \: rh$

$⟹2 \times \frac{22}{7} \times r \times h$

$⟹ \frac{22}{7} \times 2r \times h$

$⟹ \frac{22}{7} \times 84 \times 120$

$⟹22 \times 12 \times 120$

$⟹22x1440$

$⟹31680 \: sq.cm.$

Hence, the roller covers 31680 sq. Cm of the ground in one revolution.

∴ Area of the ground used in the 500 revolution

$⟹31680 \times 500$

$⟹15840000 \: sq.cm.$

$⟹ \frac{15840000}{10000}$

$⟹1584 \: sq.m.$

∴Area of the ground = 1584 sq. m