Quantitative Aptitude • Time, Speed & WorkHard
Two trains, 310 m and 80 m long, are running on parallel tracks in opposite directions at 36 km/h and 72 km/h. How long will they take to cross each other completely?
A. 39 seconds
B. 13 seconds✓ Correct Answer
C. 10.33 seconds
D. 3.61 seconds
💡 Solution & Explanation
In opposite directions, the speeds add: 36 + 72 = 108 km/h = 108 × 5/18 = 30 m/s. To cross completely, they cover both lengths: 310 + 80 = 390 m. Time = 390 ÷ 30 = 13 seconds. In the same direction the speeds would subtract instead.
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