Question

a boy is cycling such that the wheels of the cycles are making 140 revolutions per minute .if the diameter of the wheel is 50cm , calculate the speed per hour which the boy is cycling?

Answer 1

revolution per minute =140
diameter of wheel =50cm
speed per hour =?
= 140/50
=2.8

Answer 2

diameter is 50 cm
then,
radius is 25 cm
circumference is 2πr that is 2×3.14×25=157 cm
no. of revolution is 140 in one minute
means total distance covered is 140×157 cm =21980 cm = 0.2198km ≈0.22 km
in one minute
so,
0.22×60km per hour
13.2 km per hour