Question 68

A man sitting in train travelling at the rate of 50 km/h observes that it takes 9 s for a goods train travelling in the opposite direction to pass him.If the goods train is 187.5 m long,find its speed

Solution

Speed of first train = $$50\times\frac{5}{18}=\frac{125}{9}$$ m/s and speed of second train = $$x$$ m/s

Relative speed = $$(x+\frac{125}{9})$$ m/s

Length of second train = $$187.5$$ m

Using, speed = distance/time

=> $$x+\frac{125}{9}=\frac{187.5}{9}$$

=> $$x=\frac{62.5}{9}$$

$$\therefore$$ Speed of goods train = $$\frac{62.5}{9}\times\frac{18}{5}=25$$ km/hr

=> Ans - (B)

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