Question: A man walks at a speed of 4 km/h and runs at 8 km/h. If he walks for 30 minutes and then runs for 15 minutes, what is his average speed for the entire trip?

Options:

1. 5 km/h
2. 6 km/h
3. 7 km/h
4. 8 km/h

Correct Answer: 6 km/h

Solution:

Total distance = (4 km/h × 0.5 h) + (8 km/h × 0.25 h) = 2 km + 2 km = 4 km. Total time = 0.5 h + 0.25 h = 0.75 h. Average speed = Total distance / Total time = 4 km / 0.75 h = 5.33 km/h.