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प्रश्न
A cart wheel makes 9 revolutions per second. If the diameter of the wheel is 42 cm, find its speed in km/hr.
उत्तर
Circumference = 2 π r = π d
`= 22/7 xx 42`
= 132 cm = 1.32 m
Circumference= 1.32 m
No. of revolutions = 9 per second
No. of revolutions per hour = 9 x 60 x 60 = 32400
Distance covered in one hour= 32400 x 1.32 = 42768m/hour
Speed of the wheel in km/hour = `42768/1000 = 42.768` km/hour = 43 km / hr
Speed = 43 km/hr
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