Question

diameter and length of a roller are 84 cm and 120 CM respectively in how many revolutions can the ruler level the playground of area 1584 m square

Answer 1

Solution :-

Roller is in the shape of a cylinder.

Diameter = 84 cm

Radius = 84/2 = 42 cm

Area of roller = Curved surface area of cylinder = 2πrh

⇒ (2*22*42*120)/7

Curved surface area of cylinder = 31680 cm²

Area to be covered = 1584 sq m or 1584*10000

= 15840000 cm² (1 sq m = 10000 sq cm)

Total number of revolution to cover the area of 15840000 sq cm =

15840000/31680

500 revolutions 

Answer.

Answer 2

$\mathbb{GIVEN}$:
Diameter of roller is 84 cm.
length (height) of roller is 120 cm.
area of the playground = 1584 m².

We know that,
radius = $\frac{Diameter}{2}$

radius = $\frac{84}{2}$ = 42 cm

.

We know that,
1 m³ = 10000 cm³

So,
1584 m³ = 1584 × 10000 = 15840000 cm³

$\bf{Curveda\:Surface \:Area\: of\: the \:roller}$ = 2πrh

= 2 × $\frac{22}{7}$ × 42 ×120

= 31680 cm²

.

Now,
31680 cm² = 1 revolution

So,
$\frac{15840000}{31680}$ = 500 revolutions

Hence,
the roller will make 500 revolutions to level the playground.