How can I book train tickets before 30 minutes?

54 kmph

Let the speed of train A be SA = 45 kmph and that of train B be SB Then, time taken by train A = TA = 4 hours 48 minutes = 4 + 48/60 = 24/5 Time taken by train B = TB = 3 hours 20 minutes = 3 1/3 hours = 10/3 hours Using formula SA/SB = TB/TA 45/SB = 10/3 X 5/24 = 25/36 = 5/6 SB = 45 X 6/5 = 54 kmph.