Question

A boy is cycling such that the wheels of the cycle are revolving at the rate of 140 revolutions per minute. If the diameter of the wheel is 60cm then the speed per hour with which the boy is cycling is _________ km/hr

Answer 1

Perimeter of the whells
= 2πr
= 2xπx30
=188.5 cm

in one minute 140 revolutions
that means 140 x 188.5 cm distance travelled
= 26400cm

speed = 26400cm/min
= 15.8km/hr

Answer 2

Hope it's help u
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Radius of the wheel = 602=30cm602=30cm

circumference=2πr=2×227×30=13207cmcircumference=2πr=2×227×30=13207cm

Distance covered in one revolution
∴Distance covered in 140revolutions
=13207cm=13207×140cm=26400cm=26400100000km=0.264kmDistance covered in one revolution=13207cm∴Distance covered in 140 revolutions=13207×140cm=26400cm=26400100000km=0.264km

⟹Distance covered in one hour =0.264×60=15.84km≃16km/hr⟹Distance covered in one hour =0.264×60=15.84km≃16km/hr

Hence the speed is 16km/hr