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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.
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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