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Question
An express train is running between two stations with a uniform speed. If the diameter of each wheel of the train is 42 cm and each wheel makes 1200 revolutions per minute, find the speed of the train.
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Solution
radius of the wheel = `42/2` = 21 cm
Circumference of the wheel = 2π x 21 = 132 cm
Distance travelled in one minute
= 132 x 1200
= 158400 cm
= 1.584 km
Hence the speed of the train
= `[1.584 "km"]/[1/60"hr"]`
= 95.04 km/hr.
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