Train a crosses a man standing on a platform completely in a minute. train b twice as long as train a travelling in the opposite direction takes another half a minute to cross the man on the platform. how long will train a and train b take to cross each o
(91 + 3/7) sec
Answers
Let the length of train a be x mts
The length of train b will be = 2x (given train b is twice as long as train a)
As train a crosses man in a minute.
Speed of train a = Distance covered / time taken
= x / 1 (when train crosses a man standing, distance covered is equal to length of train)
= x mts /min
Again, train b crosses man in half minute
Speed of train b = 2x / 0.5
= 4x mts/min.
When both the trains crosses each other,
Total distance covered = Length of train a + length of train b (when two trains cross each other in opposite direction, total distance covered is equal to sum of lengths of two trains)
= x + 2x
= 3x
Relative speed of trains = Speed of train a + speed of train b (when two trains cross each other in opposite direction, relative speed of trains is equal to sum of speeds of two trains)
= x + 4x
= 5x mts/min
Time taken by trains to cross each other = Distance / relative speed
= 3x / 5x
= 0.6 mins
= 0.6 * 60
= 36 sec.
Hence, train a and train b will take 36 seconds to cross each other.