Question

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.

Answer 1

Answer:

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

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

Step-by-step explanation:

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Answer 2

Answer:

Step-by-step explanation:

Here is your solution......

(A) length of train=120m

(B) Speed of train=54kmph

Explain....

(1) Asume L is the length of the train and S is the Speed

(2) Speed of the train will be S = (180+L)/20

(3) Assuming that S is constant, and knowing that the train takes 8 sec to pass a single point (the man), then:

S = L / 8

(4) 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

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