To answer 3d, we need to calculate the average speed for the entire journey.

Step-by-Step Solution:

1. Formula for Average Speed: $\text{Average Speed} = \frac{\text{Total Distance}}{\text{Total Time}}$

2. Total Distance: From part 3c, the total distance traveled is: $\text{Total Distance} = 1600 + 3200 + 3200 = 8000 \, \text{m}.$

3. Total Time: From the graph:

   • Total time is from $t = 0 \, \text{s}$ to $t = 160 \, \text{s}$. $\text{Total Time} = 160 \, \text{s}.$

4. Average Speed: Substitute the values: $\text{Average Speed} = \frac{8000}{160} = 50 \, \text{m/s}.$

Final Answer:

The average speed for the journey is: $\boxed{50 \, \text{m/s}}$

Let me know if you want further clarification or have any additional questions!

Expanding Questions:

1. How is the concept of average speed different from instantaneous speed?
2. Can you explain why the total distance includes multiple sections?
3. Why is the distance during uniform motion a rectangle on a speed-time graph?
4. How would the calculation change if there was a different acceleration?
5. Can you calculate average velocity for this journey if there was a direction involved?

Tip:

Always remember, the area under a speed-time graph represents the total distance traveled!