Question

Two trains starts simultaneously from P & Q towards Q & P respectively at 8 am.They cross each other at 12 noon.Train starting from Q,thereafter takes 6hrs to reach P.On a particular day,the train starting from P,reduced its speed and arrived at Q ,200 min later.At what time did the train crosses each other on that day?

Answer 1

This is hard. I found this answer online:


Taking the trains as point masses (as crossing time is negligible ) ...
The train starting from Q takes 6 hrs to reach P and 4 hours (12-8 ) to reach the points where they meet so we can say that it travels 2/3 distance by that time. Which means the train starting from P takes 4 hrs to reach 1/3 and 12 hours=720 min to reach Q.
Now it reduces its speed and reaches Q after 920 min but the other train still takes 360 min
So their speed ratio is 920:360=23:9
So the faster one travels 23/32 distance when they meet which will take 23*360*60/32 sec=15525 secs= 4 hr 18 min 45 secs
Which is 12:18:45