Banking Notes / Quantitative Aptitude / Chapter 17
Chapter 17 of 26

Problems on Trains

Train crossing platforms, poles, and other trains — the most common speed-distance variant tested in bank prelims.

📖 ~8 min read 🏦 Banking Quantitative Aptitude

Introduction

Train problems are Time-Speed-Distance questions with one twist: the length of the train itself must be added to the distance covered whenever the train crosses something (a pole, a platform, or another train).

Core Rules

ScenarioDistance Covered
Train crosses a pole/point objectLength of the train
Train crosses a platform/bridgeLength of train + Length of platform
Two trains cross each other (opposite direction)Sum of both lengths, at (speed1+speed2)
Two trains cross each other (same direction)Sum of both lengths, at (speed1−speed2)
Q. A train 150 m long crosses a pole in 10 seconds. Find its speed in km/hr.
Speed = Distance/Time = 150/10 = 15 m/s. Convert: 15 × 18/5 = 54 km/hr.
Q. A train 200 m long crosses a platform 300 m long in 25 seconds. Find the speed of the train.
Total distance = 200+300 = 500 m. Speed = 500/25 = 20 m/s (= 72 km/hr).
Q. Two trains 100 m and 150 m long run in opposite directions at 30 km/hr and 20 km/hr. Find the time they take to cross each other.
Relative speed = 30+20 = 50 km/hr = 50×5/18 = 125/9 m/s. Total length = 100+150 = 250 m. Time = 250 ÷ (125/9) = 250×9/125 = 18 seconds.
⚠️ Key Insight: "Crossing a man/pole" only involves the train's own length; "crossing a platform" always requires adding the platform's length — mixing these up is the single most common mistake.
✅ Practice Focus: Pole/point-crossing speed calculation · Platform-crossing distance · Two-trains-crossing in same and opposite directions.

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