Two outposts M and N are 320 km apart. Train A leaves M for N at 40 km/h at 6:00 AM. Train B leaves N for M at 60 km/h at 8:00 AM. At what time will they cross? MCQ with Answer and Explanation
Two outposts M and N are 320 km apart. Train A leaves M for N at 40 km/h at 6:00 AM. Train B leaves N for M at 60 km/h at 8:00 AM. At what time will they cross?
A. 10:24 AM
B. 10:12 AM
C. 10:36 AM
D. 10:48 AM
Answer: Option A
Solution (By JKSSB Mock Tests)
By 8:00 AM, Train A has run for 2 hours, covering 40 * 2 = 80 km. Remaining separation distance = 320 - 80 = 240 km. Relative speed = 40 + 60 = 100 km/h. Time after 8:00 AM = 240 / 100 = 2.4 hours = 2 hours 24 minutes. Meeting time = 8:00 AM + 2 hours 24 minutes = 10:24 AM.
Explanation:
By 8:00 AM, the first person covers 40 * 2 = 80 km. Relative speed = 60 - 40 = 20 km/h. Time to meet = 80 / 20 = 4 hours. Distance from A = Speed of second person * Time = 60 * 4 = 240 km.
Two standard vehicles depart a warehouse at the same instant at a right angle. Their speeds are 45 km/h and 60 km/h. Find the direct distance separating them after 20 minutes.
Explanation:
Time = 20 minutes = 1/3 hours. Distance covered by first vehicle = 45 * (1/3) = 15 km. Distance covered by second vehicle = 60 * (1/3) = 20 km. Direct line distance = sqrt(15^2 + 20^2) = sqrt(225 + 400) = sqrt(625) = 25 km.
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