Question

A roller of diameter 0.9m and length 1.8m is used to press the ground . Find the area of the ground pressed by it in 500 revolutions. Use (π = 3.14) only .

Answer 1

The roller is always in cylindrical shape

Diameter of roller= 0.9m

Therefore, radius =d/2=0.9/2=0.45m

Length=Height=1.8m

Now, Curved surface area of cylindrical roller= 2πrh

=2x3.14x0.45x1.8

=5.0868m^2

1 revolution of roller covers 5.0868 m^2 of ground

Therefore, 500 revolutions =5.0868x500

=2543.4 m^2

Answer 2

Explanation:

Given:

Central angle, θ = 144°

Diameter of the circle = 10 cm

∴ Radius of the circle =

10

2

cm = 5 cm

We have to find the length of the arc (l) of the circle.

We know:

Length of an arc, l =

θ

360

×2πr

Thus, we have:

Length of the arc, l = 5cm

144

360

×2×3.14×5 cm

= 12.56 cm