A train Meerut at 6 a.m. and reaches Delhi at 10 a.m. another train leaves Delhi at 8 a.m. and reaches Meerut at 11:30 a.m. at what time do trains cross one another?

Let the distance between Meerut and Delhi be y km.
Average speed of the train leaving Meerut = y/4 km/hr.
Average speed of the train leaving Delhi = 2y/7 km/hr.
suppose they meet x hrs. after 6 a.m
then, xy/4 + 2y (x-2)/7 = y
⇒ x/4 + 2x-4/7 = 1
⇒ 15x = 44
∴ x = 44/15 = 2 hrs. 56 min
So, the train meet at 8:56 a.m