Correct Answer - Option 1 :
\(\dfrac{23}{3}\) sec
Given-
Length of 1st train = 110 m
Speed of 1st train = 72km/hr
Length of 1st train = 120 m
Speed of 1st train = 36 km/hr
Formula used =
Distance = Speed × Time
Relative Speed = Speed of Object 1 + Speed of Object 2 ( If they are moving opposite to each other)
Concept Used-
For a train to cross another train completely it should travel a distance equal to sum of length of both the trains.
Calculation-
Total distance to be covered = 110 + 120
= 230 m
Speed of 1st train = 72 × 5/18
= 20 m/sec
Speed of 1st train = 36 × 5/18
= 10 m/sec
Their relative Speed = 20 + 10
= 30 m/sec
Time taken to cross each other = 230/30
= 23/3 seconds