Question

Train a takes 45 minutes more than train b to travel a distance of 450 km. Due to engine trouble speed of train b falls by a quarter, so it takes 30 minutes more than train a to complete the same journey. What is the speed of train a (in km/hr)?

Answer 1

Answer:

The speed of train A is 100 km/h.

Step-by-step explanation:

va * ta = 450,   vb * tb = 450,  ta = tb + 3/4

( 3/4 h = 45 min )

Also:

3/4 vb ( ta + 1/2 ) = 450

3/4 * 450/tb ( ta + 1/2 ) = 450  / : 450

3/4tb ( ta + 1/2 ) = 1   / *4 tb

3 ta + 3/2 = 4 tb

3 * ( tb + 3/4 ) + 3/2 = 4 tb

3 tb + 9/4 + 6/4 = 4 tb

tb = 15/4 h

ta= 15/4 + 3/4 = 18/4 = 4.5 h

va = 450 km : 4.5 h = 100 km/h