86. Two trains of equal lengths take 10 seconds and 15 seconds respectively to cross a telegraph post. If the length of each train be 120 metres, in what time (in seconds) will they cross each other travelling in opposite direction?

By Admin / September 6, 2025

[A]. 10

[B]. 12

[C]. 15

[D]. 20

✅ The correct answer is option B.
Speed of the first train =

120

m/sec = 12 m/sec.

Speed of the second train =

120

m/sec = 8 m/sec.

Relative speed = (12 + 8) = 20 m/sec.

Required time =

(120 + 120)

sec = 12 sec.

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