Question

If two trains of same length traveling in opposite direction and If one train passes a pole in T1 seconds and second train in T2 seconds, then time to crossing the trains,
    = (2 x T1 x T2) / (T1 + T2) seconds.​

Answer 1

Answer:

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Speed becomes ¾ hence time becomes 4/3 -------------------- remember (S1 / S2) = (t2 / t1))

-----> increased time is 1/3 = 20 minutes. So original time = 60 minutes. (1 belongs to 20mins, then 3 belongs to 60mins)

In other words

------> speed dropped to 75% and time increased to 133.33% ----> increased time = 33.33% = 20 minutes

Now 33.33 % belongs to 20 minutes, So 100% belongs to 60 minutes.

Answer 2

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If both trains are traveling in same directions then, T = (2 x t1 x T2)/difference of T1 and T2

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