Ashish travels a distance of 100 km in the following manner, at 20 kmph for the 1st 50 kms, at 25 kmph for the next 50 kms. He returns at a constant speed of 25kmph. What was his average speed for the journey?

Forward journey: 50 km at 20 kmph = 2.5 hours, 50 km at 25 kmph = 2 hours. Total forward time = 4.5 hours. Return journey: 100 km at 25 kmph = 4 hours. Total distance = 200 km, total time = 8.5 hours. Average speed = 200/8.5 = 23.52 kmph. Average speed is always total distance divided by total time, not the average of individual speeds.