Train A travelling at 60km/hr leaves Mumbai for Delhi at 6 p.m. Train B travelling at 90 km/hr also leaves Mumbai for Delhi at 9 p.m. Train C leaves Delhi for Mumbai at 9 p.m. If all the three trains meet at the some time between Mumbai and Delhi, then what is the speed of Train C if the distance between Delhi and Mumbai is 1260 km?

Distance travelled by train A in 3 hours (till 9 p.m.) travelling at 60 km/hr = $$60\times3=180$$ km

Relative speed of Train A and B travelling in same direction = $$90-60=30$$ km/hr

Now, time when train A and train B will meet (Train C will also meet at this point, given) = $$\frac{180}{30}=6$$ hours

Thus, they will meet at 3 a.m. at a distance of $$(90\times6)=540$$ km from Mumbai = $$1260-540=720$$ km from Delhi.

$$\therefore$$ Speed of train C = $$\frac{720}{6}=120$$ km/hr

=> Ans - (C)