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A man is standing on a railway bridge which is 180m long. He finds that a train crosses the bridge in 20seconds but himself in 8 seconds. Find the length of the train and its speed.

Read Solution (Total 2)

length of train=120m
Speed of train=54kmph

Explanation;
Asume L is the length of the train and S is the Speed
Speed of the train will be S = (180+L)/20

Assuming that S is constant, and knowing that the train takes 8 sec to pass a single point (the man), then:
S = L / 8
We now have two different ways of deriving S, both of which use L. So we can say that
(180 + L) / 20 = L / 8. Solving this L is 120. Substitute this in any one of the equation S will 45kmph
13 years agoHelpfull: Yes(7) No(3)

Let the length of the train be x meters Then, the train covers x meters in 8 seconds and (x + 180) meters in 20 seconds. Therefore x/8 = (x+180)/20 20x = 8(x+180) x = 120 Therefore Length of the train = 120m Speed of the train = 120/8 m/sec = 15 m/sec =15 * 18/5 kmph = 54kmph

ans: 120m and 54km/h
10 years agoHelpfull: Yes(0) No(0)

Wipro Other Question

Rajesh traveled from city A to city B covering as much distance in the second part as he did in the first part of this journey. His speed during the second part was twice as that of the speed during the first part of the journey. What is his average speed of journey during the entire travel?

(1) His average speed is the harmonic mean of the individual speeds for the two parts.
(2) His average speed is the arithmetic mean of the individual speeds for the two parts.
(3) His average speed is the geometric mean of the individual speeds for the two parts.
(4) Cannot be determined. A train running at 54 kmph takes 20 seconds to pass a platform. Next it takes 12 seconds to pass a man walking at 6 kmph in the same direction in which the train is going. Find the length of the train and the length of the platform.