Find the average speed when the first half of a journey is done at a speed of 60 km/h and the second half ata speed of 40 km/h.

Speed for the first half of the journey = 60 km/h

Speed for the second half of the journey = 40 km/h

The formula for the average speed when the distance is the same but speeds are different is:

​$$\text{Average speed} = \frac{2 \times \text{Speed}_1 \times \text{Speed}_2}{\text{Speed}_1 + \text{Speed}_2}$$​​

 the speed for the first half of the journey be 60 km/h

the speed for the second half be 40 km/h.

Using the formula for average speed:

​$$\text{Average speed} = \frac{2 \times 60 \times 40}{60 + 40} \\ \ \\\text{Average speed} = \frac{2 \times 2400}{100} \\ \ \\\text{Average speed} = \frac{4800}{100} = 48 \text{km/h}$$​​

Thus, the average speed for the entire journey is 48 km/h.