Train A takes 1 hour more than train B to travel a distance of 720 km. Due to engine trouble speed of train B falls by a third, so it takes 3 hours more than Train A to complete the same journey? What is the speed of Train A (in km/hr)?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 80
Let the train A's speed be x km/hr
Let train B's speed be y km/hr
720/x - 720/y = 1 .....(1)
720/(2y/3) - 720/x = 3 .....(2)
adding (1) and (2), we get
360/y = 4
y = 90
putting y = 90 in (1)
720/x - 720/90 = 1
x = 80