Two trains are moving in the same direction at 50 km/hr and 30 km/hr. The faster train crosses a man in the slower train in 18 seconds. Find the length of faster train.
Answer: B
Crossing a man in the other train covers only the faster train's length.
\[ \text{relative speed} = 50 - 30 = 20 \text{ km/hr} = 20 \times \frac{5}{18} = \frac{50}{9} \text{ m/s} \]
\[ L = \frac{50}{9} \times 18 = 100 \text{ m} \]
The slower train's length is irrelevant, because the reference point is a single person, not the whole train.
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