Question

A cylindrical roller is a length 2m and diameter 84cm.Find the number of revolutions it has to make to cover an area of 7920sq.m

Answer 1

h = 2 m
d = 84 cm = 0.84 m
r = 0.42 m

Curved surface area = 2πrh
= 2 × 22/7 × 42/100 × 2
= 5.28 sq. m

Revolutions made = 7920/5.28 = 1500

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Answer 2

Given:

A cylindrical roller is a length 2m and diameter 84cm

To Find:

Find the number of revolutions it has to make to cover an area of 7920sq.m

Solution:

A cylinder is a 3-dimensional structure with two circular bases and a height between the bases.

The curved surface area of a cylinder is found by using the formula,

$CSA=2\pi rh$

where r is the radius of the base and h is the height.

Now it is given that a cylindrical roller make revolutions to cover an area of 7920 sq.m we need to calculate the number of revolutions need,

First, we will calculate the area covered in a revolution which will be equal to the curved surface area, given radius=84/2=42cm=0.42m and height=2m

$CSA=2*\frac{22}{7}*0.42*2\\ =5.28m^2$

Now the number of revolutions will be,

$Revolution=\frac{7920}{5.28}\\ =1500$

Hence, 1500 revolution is needed to cover 7920 sq.m area.