1. **State the problem:** A man starts a journey at 0900 hours and completes it at 1600 hours, covering a distance of 140 km. We need to find his average speed. 2. **Formula used:** Average speed is calculated by dividing the total distance traveled by the total time taken. $$\text{Average speed} = \frac{\text{Total distance}}{\text{Total time}}$$ 3. **Calculate total time:** The journey starts at 0900 hours and ends at 1600 hours. $$\text{Total time} = 1600 - 0900 = 7 \text{ hours}$$ 4. **Calculate average speed:** Using the formula, $$\text{Average speed} = \frac{140}{7}$$ 5. **Simplify the fraction:** $$\text{Average speed} = \frac{\cancel{140}}{\cancel{7}} = 20 \text{ km/h}$$ 6. **Conclusion:** The man's average speed during the journey is 20 km/h.