We are given the following information:

1. A car leaves Johannesburg at 14:00 traveling at 64 km/h.
2. A truck leaves Johannesburg one hour later at 15:00, and the car and truck maintain constant speeds.
3. By 16:30, the car is 70 km ahead of the truck.

We need to find the speed of the truck.

Step-by-step breakdown:

1. Time traveled by the car by 16:30:

   • The car leaves at 14:00 and the comparison is at 16:30, so the car travels for $2.5$ hours.

   $\text{Distance traveled by the car} = 64 \, \text{km/h} \times 2.5 \, \text{hours} = 160 \, \text{km}$

2. Time traveled by the truck by 16:30:

   • The truck leaves at 15:00 and the comparison is at 16:30, so the truck travels for $1.5$ hours.

   $\text{Let the speed of the truck be } v \, \text{km/h}.$ The distance traveled by the truck will be: $\text{Distance traveled by the truck} = v \, \text{km/h} \times 1.5 \, \text{hours} = 1.5v \, \text{km}$

3. Distance difference:

   • At 16:30, the car is 70 km ahead of the truck, so: $160 \, \text{km} - 1.5v \, \text{km} = 70 \, \text{km}$

4. Solve for $v$: $160 - 1.5v = 70$ $1.5v = 160 - 70$ $1.5v = 90$ $v = \frac{90}{1.5} = 60 \, \text{km/h}$

Thus, the speed of the truck is 60 km/h.

Do you need more details on any part of the solution or have any questions?

Here are some related questions you might find interesting:

1. How would the problem change if the truck left 2 hours later instead of 1 hour?
2. What if the truck's speed was unknown, but the time difference was only 30 minutes?
3. How would you calculate the time taken for the truck to catch up to the car?
4. What if the car's speed was increased by 10 km/h? How would that affect the final answer?
5. How would the problem change if both vehicles traveled different distances instead of from the same starting point?

Tip:

In word problems, always carefully track when each object starts moving and for how long each travels!