A train starts from A at 6 AM andreaches B at 11 AM on the same day. Anothertrain starts from B at 8 AM and reaches A at 3 PM on the same day. At what time the two trains will have crossed each other?
Answer & explanation
Correct answer: option 1
Since, the first train that travels from A to B covers the distance D in 5 hour
Since, the second train that travels from B to A covers the distance D in 7 hour
So , Ratio of A B
Time 5 : 7
Speed 7 : 5
( Speed is inversely proportional to time )
LCM of ( 7,5) = 35 km
A alone travels till 8:00 am . so , Distance traveled by A in 2 hours
= 7 × 2 = 14 km
Remaining Distance = 35 - 14 = 21 km
Let Speed of A = 7 km/h & Speed of B = 5 km/h
Relative speed when moves in opposite direction = 7 + 5 = 12 km/h
Time = \(\frac{Distance}{Speed}\)
= \(\frac{21}{12}\)
= 1.75
= 1 hour 45 minutes
So , They will cross each other at = 8:00 am + 1 hour 45 minutes
= 9:45 am