From P and Q, two trains start moving towards each other at the same time. Their speeds are 120 km/hr and 100 km/hr, respectively. When the two trains meet each other, one train has covered 40 km more than other train. Find the distance between P and Q in Kms?

440

Total distance travelled by two trains in the end of the 1st hour = 1st - 120 km and 2nd - 100 km (Difference between 2 trains is 20km)

Total distance travelled by two trains in the end of the 2nd hour = 1st - 240 km and 2nd - 200 km (Difference between 2 trains is 40km)

Thus, distance between P and Q when the difference in the distance travelled by 2 trains is 40 km: 240 + 200 = 440 kms