Trains

Train-crossing problems — where the train's own length must be added to the distance covered.

📖 ~4 min read 📐 RRB NTPC / Group D — Mathematics

Scenario	Distance Covered
Train crosses a pole/point object	Length of the train
Train crosses a platform/bridge	Length of train + Length of platform
Two trains cross (opposite direction)	Sum of both lengths, at (speed1+speed2)
Two trains cross (same direction)	Sum of both lengths, at (speed1−speed2)

💡 Example: A 150 m train crosses a pole in 10 sec. Speed = 150/10 = 15 m/s = 54 km/hr.

⚠️ "Crossing a pole/man" uses only the train's own length; "crossing a platform" adds the platform's length too — this is the most common mix-up.

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