Quantitative Aptitude • Time, Speed & WorkHard
Two trains, 280 m and 420 m long, are running on parallel tracks in opposite directions at 54 km/h and 72 km/h. How long will they take to cross each other completely?
A. 8 seconds
B. 5.56 seconds
C. 140 seconds
D. 20 seconds✓ Correct Answer
💡 Solution & Explanation
In opposite directions, the speeds add: 54 + 72 = 126 km/h = 126 × 5/18 = 35 m/s. To cross completely, they cover both lengths: 280 + 420 = 700 m. Time = 700 ÷ 35 = 20 seconds. In the same direction the speeds would subtract instead.
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