2. A biker rode up a 20 km hill in 2 hours and down the hill in 0.5 hour
without stopping. What was his average speed:
- going up the hill
- going down the hill?
the whole trip?

(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