RRB Group-D Model Paper 18 with answers for online practice

GIVEN:
Two speeds of train is 60 k/hr and 90 km/hr
FORMULAE USED:
Average Speed = Total distance/total time taken
SOLUTION:
Total Distance = 2X
Total time = (X/60) + (X/90)
Average speed = 2X/(5X/180) = 2 × (180/5)
⇒ 72 km/hr
∴ Average speed of the train is 72 km/hr