A train 120 m long travels at constant speed and passes a pole in 8 seconds. How long does it need to cross a bridge 180 m long, from the front entering to the rear leaving?
Answer and explanation
Correct answer: C. 20 seconds
- Step 1: Speed = 120 m / 8 s = 15 m/s.
- Step 2: To cross the bridge the train covers its own length plus the bridge: 120 + 180 = 300 m, so t = 300 / 15 = 20 s.
Answer
20 seconds.
Why not the others: Using 180 m alone forgets the train length; the other values rest on a wrong speed or a wrong scaling.
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