Mathematics

The wheel of the engine of a train $4\dfrac{2}{7}$ m in circumference makes 7 revolutions in 3 seconds. Find the speed of the train in km per hour.

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Given,

Circumference of wheel = $4\dfrac{2}{7} \text{ m} = \dfrac{30}{7}$ m.

Number of revolutions = 7

Time = 3 seconds

We know that,

Distance = circumference × revolutions

= $\dfrac{30}{7}$ × 7

= 30 m.

So the train moves 30 m in 3 seconds.

Speed = $\dfrac{Distance}{Time}$

= $\dfrac{30}{3}$ = 10 m/s.

1 m/s = 3.6 km/h

10 m/s = 10 × 3.6 km/h = 36 km/h

Hence, speed of the train = 36 km per hour.

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