Question

diameter and length of a roller are 84 cm and 120 cm respectively . in how many revolution can the roller level the playground of area 1,584msq.

Answer 1

shape of roller is generally cylindric.
diameter(d) = 84cm.
radius(r) = d/2 = 42cm.
length(l) = 120cm.
curved surface area of roller = 2πrl = 2x(22/7)x42x120 = 44x720 cm².
in one revolution it will level the area equal to its curved surface area.
lets assume it takes n revolution to level the play ground.
area of playground = 1584m². = 15840000cm².

so, 44x720n = 15840000
n = 500.

Answer 2

✬ Number of revolutions = 5 ✬

Step-by-step explanation:

Given:

• Diameter of roller is 84 cm.
• Length of roller is 120 cm.
• Area of roller is 1584 m².

To Find:

• In how many revolutions the roller will level the playground?

Solution: As we know that

• Radius = Diameter/2
• Radius of roller = 84/2 = 42 cm

Now, We have to find the curved surface area of the roller ➫

★ CSA = 2πrh sq units ★

$\implies{\rm }$ CSA of roller = 2 x 22/7 x 42 x 120 cm²

$\implies{\rm }$ 2 x 22 x 6 x 120 cm²

$\implies{\rm }$ 31680 cm²

So, the curved surface area of roller is 31680 cm²

But area of playground is 1584 m²

• Area of playground in cm² = 1584 x 100 = 158400 cm²

∴ Number of revolutions made by roller =

$\implies{\rm }$ 158400/31680

$\implies{\rm }$ 5 revolutions.

Hence, the roller will make 5 revolutions to cover playground.