A boy is cycling in such a way that the wheels of his bicycle are making 140 revolutions per minute. If the diameter of a wheel is 60 cm, calculate the speed (in km / hr) at which the boy is cycling.
Diameter of the wheel = 60 cm
Therefore, Radius of the wheels = 30 cm
Circumference of the wheels =2πr=2×227×30=13207 cm
Distance covered by the wheel in 1 revolution = 13207 cm
Therefore, Distance covered by the wheel in 140 revolutions =(13207×140×1100) m
=(1320×1407×100×11000) km=2641000 km
Now,
Distance covered by the wheel in 1 minute = Distance covered by the wheel in 140 revolution =2641000 km
Therefore, Distance covered by the wheel in 1 hour = 2641000×60=15.84 km/h
Hence, the speed at which the boy is cycling is 15.84 km/h