DRDO Multi tasking staff Model paper 1

let the time taken by train B be x
⇒ Time taken by train A = x + 1
⇒ New speed of train B = ⅔ × original speed
⇒ Time taken by train after engine problem = 3x/2 [Time ∝ 1/speed]
ATQ,
This is 3 hours more than time taken by A
⇒ 3x/2 = x + 1 + 3
⇒ x/2 = 4
⇒ x = 8
⇒ Time taken by A = x + 1 = 9
∴ Speed of A = distance/time = 720/(8 + 1) = 80