Problem:
A car goes from town A to another town B with a speed of 40 km/h and returns back to the town A with a speed of 60 km/h. The average speed of the car during the complete journey is *?

Solution:
To find the average speed of the car during the entire journey, we need to first understand what is meant by average speed. Average speed is defined as the total distance traveled divided by the total time taken.

Step 1: Calculate the distance between town A and town B. Let's assume the distance is 'd' km.

Step 2: Calculate the time taken by the car to travel from town A to town B. Let's assume the time taken is 't1' hours.

We know that speed = distance/time
Therefore, time = distance/speed

So, the time taken by the car to travel from town A to town B is:
t1 = d/40

Step 3: Calculate the time taken by the car to return to town A from town B. Let's assume the time taken is 't2' hours.

Similarly, the time taken by the car to return from town B to town A is:
t2 = d/60

Step 4: Calculate the total time taken by the car for the entire journey. Let's assume the total time taken is 'T' hours.

The total time taken by the car for the entire journey is the sum of the time taken to travel from town A to town B and the time taken to return from town B to town A:
T = t1 + t2
= d/40 + d/60
= 3d/120 + 2d/120
= 5d/120
= d/24

Step 5: Calculate the average speed of the car for the entire journey. Let's assume the average speed is 'S' km/h.

We know that average speed = total distance/total time
In this case, the total distance is 2d (since the car travels the same distance twice) and the total time is T. So, we have:
S = 2d/T
= 2d/(d/24)
= 48 km/h

Therefore, the average speed of the car during the complete journey is 48 km/h.