Two trains 120 meters and 80 meters long are running along parallel tracks in the same direction at speeds of 46 km/h and 36 km/h respectively. In what time will the faster train cross the slower train completely? MCQ with Answer and Explanation
Two trains 120 meters and 80 meters long are running along parallel tracks in the same direction at speeds of 46 km/h and 36 km/h respectively. In what time will the faster train cross the slower train completely?
A. 64 seconds
B. 80 seconds
C. 72 seconds
D. 90 seconds
Answer: Option C
Solution (By JKSSB Mock Tests)
Total distance = 120 + 80 = 200 meters. Relative speed in same direction = 46 - 36 = 10 km/h = 10 * (5/18) = 25/9 m/s. Time required = 200 / (25/9) = 200 * 9 / 25 = 8 * 9 = 72 seconds.
Two points M and N are separated by 300 km. At 8:00 AM, a car leaves M for N at 60 km/h. At 9:00 AM, another car leaves N for M at 90 km/h. At what time will they pass each other?
Explanation:
By 9:00 AM, the first car covers 60 km * 1 hour = 60 km. The remaining distance between them is 300 - 60 = 240 km. Relative speed = 60 + 90 = 150 km/h. Time to meet after 9:00 AM = 240 / 150 = 8/5 hours = 1 hour 36 minutes. Meeting time = 9:00 AM + 1 hour 36 minutes = 10:36 AM.
Explanation:
New speed = 7/8 of usual speed => New time = 8/7 of usual time. Difference = 1/7 of usual time = 10 minutes. Usual time = 10 * 7 = 70 minutes.
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