Question

4.
Two trains running in opposite directions cross a man standing on the platform in 27 seconds and 17 seconds respectively and they cross each other in 23 seconds. The ratio of their speeds is:

A. 1 : 3
B. 3 : 2
C. 3 : 4
D. None of these​

Answer 1

Answer:

The poet of the poem "Where do all the teachers go" is _________

Answer 2

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⠀⠀⠀⠀⠀⠀Ⱥղડաꫀɾ :-

Remember the formula for finding speed.

Speed = Distance/Time.

Therefore, Distance = Speed x Time.

If a train crosses a man/pole/post/tree in T seconds, and speed of the train is S m/s, then

Then, the Length of the Train = (Speed x Time) = ST metres.

Note: Here, the distance traveled by train in T seconds at the Speed of S m/s is equal to the length of the train.

Now, lets come to the given problem.

Let speed of the first train = X.

Time taken taken by the first train to cross a man = 27 seconds.

Therefore, Length of the first train = Speed x Time = X x 27 = 27X metres.

Let speed of the second train = Y.

Time taken taken by the second train to cross a man = 17 seconds.

Therefore, Length of the second train = 17Y metres.

Important Formula:

If two trains of length a metres and b metres are moving in opposite directions at u m/s and v m/s, then:

The time taken by the trains to cross each other

= (a + b) / (u + v) sec.

Given that, (a + b) / (u + v) = 23 seconds.

Here, a = 27X, b = 17Y and u = X, v = Y.

Therefore, (27X + 17Y)/(X + Y) = 23.

↪ 27X + 17Y = 23X + 23Y

↪ 4X = 6Y

↪ X/Y = 6/4 = 3/2

↪ X : Y = 3 : 2.

@ Aꪀցꫀl

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