To find the average speed of the entire journey, we need to use the formula:

$\text{Average Speed} = \frac{\text{Total Distance}}{\text{Total Time}}$

Step 1: Calculate the total distance traveled

• In the first part of the journey, Zak drove 60 km.
• In the second part of the journey, he drove at 102 km/h for 2 hours.

So, the distance covered in the second part is:

$\text{Distance}_2 = 102 \, \text{km/h} \times 2 \, \text{hours} = 204 \, \text{km}$

Thus, the total distance is:

$\text{Total Distance} = 60 \, \text{km} + 204 \, \text{km} = 264 \, \text{km}$

Step 2: Calculate the total time taken

• For the first part, the time taken is calculated as:

$\text{Time}_1 = \frac{\text{Distance}_1}{\text{Speed}_1} = \frac{60 \, \text{km}}{80 \, \text{km/h}} = 0.75 \, \text{hours}$

• For the second part, Zak took 2 hours, as given.

So, the total time is:

$\text{Total Time} = 0.75 \, \text{hours} + 2 \, \text{hours} = 2.75 \, \text{hours}$

Step 3: Calculate the average speed

Now, using the formula for average speed:

$\text{Average Speed} = \frac{264 \, \text{km}}{2.75 \, \text{hours}} = 96 \, \text{km/h}$

Thus, the average speed for the whole journey is 96 km/h.

Would you like more details on any step or have questions?

Here are some related questions to explore:

1. How does changing the second part of the journey's speed affect the average speed?
2. What if Zak had driven the first part at 100 km/h instead of 80 km/h?
3. How does the total distance affect the average speed?
4. If Zak took a break for 30 minutes during the journey, how would this impact the calculation?
5. How can we calculate average velocity if Zak changed direction during the journey?

Tip: Remember, average speed depends only on total distance and total time, not on how the speed varies at different parts of the journey!