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Question
The wheel of a car makes 10 revolutions per second. If its diameter is 70cm, find the speed of the car in km per hr.
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Solution
The Circumference of a Circle with diameter d is πd
The Circumference of a Circle with diameter 70cm is π x 70
= `(22)/(7) xx 70`
= 22 x 10
= 220cm
Total distance moved in 10 revolutions
= 2.2km
= 2200cm
distance moved in 1 second = 2200cm
⇒ distance moved in 1 hour
= 2200cm x 60 x 60
= 7920000cm
= `(7920000)/(100 xx 1000)`
= 79.2km
∴ Speed = 79.2km/hr.
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