Train A takes 45 minutes more than train B to travel a distance of 450 km Due to engine trouble spee...........

Quantitative Aptitude (CGL) Time & distance

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)?

120

100

110

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Explanation:

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