When 2nd train starts i.e. at 7 AM (1 hr after 6 AM ), distance covered by first train is 60 km (i.e. in 1 hr). Now 2nd train also starts and distance between them is now (480−60)=420 km Both coming in opposite direction, so relative speed =(60+80)=140 km /hr So time = 7:00 AM + (