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