How much time will the train Chennai express will take to cross another train Rajdhani running in opposite direction?
1) Train Chennai express crosses a signal pole in 12 seconds
2) Ratio of speed of train Chennai express and Rajdhani is 2:3
3) Length of two trains together is 500 meters
a) 1 only
b) 2 only
c) 1 and 3 only
d) All 1, 2 and 3 needed
e) Can’t be determined
From statement 1: nothing can be deduced from this
From statement 2: Let the speed of train Chennai express and Rajdhani be 2x and 3x respectively. Hence, if they are moving towards each other, the relative speed = 2x+3x = 5x
From Statement 3: we know the sum of the lengths of the train, however, we don't know the exact speed of any train or the exact length of any train. hence we cannot determine the time taken.
hence option e is the correct answer.