Question

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

Answer 1

Diameter = 84 cm
Radius = 84/2 = 42 cm = 0.42

Length = 2 m

CSA of cylinder = 1 Revolution
2πrh = 2 x 22/7 x 0.42 x 2 = 5.28 sq m

5.28 sq m = 1 Revolution
7920 sq m = ?
Total number of revolutions = 7920/5.28 = 1500