Answer:
(up) 10 km/hr, (down) 40 km/hr, (total) 16 km /hr
Explanation:
They went 40 km in 2.5 hours (20 km in 2 hours up, 20 km in 0.5 hrs down), so for the total trip his average speed was: 40 km/2.5hrs or 16 km/hr. Going up the hill their average time was 20 km/2hrs or 10 km/hr. Going down the hill their average speed was 20 km/0.5hrs or 40km/hour