Reena travels in three distinct phases: i. 3 hours @ 20 km/h covering 60 km ii. 2 hours @ 30 km/h covering 60 km iii. 2 hours @ 40 km/h covering 80 km Average speed of Reena = Total distance/Total time =
200
7
= 28.57 km/h Note that this average speed is different from the average of the given speeds, which is equal to 30 km/h.