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A train takes 18 seconds to pass completely through a station 162 metres long and 15 seconds to pass completely through another station 120 metres long. Find the speed of train in km per hr.
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- 50.4 kmph
- 52 kmph
- 55 kmph
- 60 kmph
Correct Option: A
Let the length of the train be x metres
Then, in 18 sec. the train travels (x + 162) metres ...(i)
and in 15 sec. the train travels (x + 120) metres
∴ In (18 – 15) = 3 sec. the train travels (x + 162)
– (x + 120) = 42m.
| ∴ In 1 sec the train travels = | = 14 metres. ...(ii) | |
| 3 |
∴ In 18 sec. the train travels = 14 × 18 = 252 metres ...(iii)
From equations (i) and (iii)
∴ x + 162 = 252
⇒ x = 252 – 162 = 90
∴ Length of the train = 90 metres
Also, from equation (ii) we see
that in 1hr. the train travels
= 14 × 60 × 60 metres
| = | km = 50.4 km | |
| 1000 |
∴ The speed of the train
= 50.4 km per hr.
