Assuming the problem is: A car travels from point A to B at 60 km/h and returns from B to A at 40 km/h. What is its average speed for the entire journey?

The key to solving this is remembering that average speed = total distance traveled / total time taken, not the arithmetic mean of the two speeds.

Let’s denote the distance between A and B as (d) km.

• Time taken to go from A to B: (t_1 = \frac{d}{60}) hours (since time = distance/speed).
• Time taken to return from B to A: (t_2 = \frac{d}{40}) hours.

Total distance for the round trip: (2d) km.

Total time: (t_1 + t_2 = \frac{d}{60} + \frac{d}{40}). To add these fractions, use a common denominator (120):
[t_1 + t_2 = \frac{2d + 3d}{120} = \frac{5d}{120} = \frac{d}{24}]

Average speed = total distance / total time:
[ \text{Average speed} = \frac{2d}{\frac{d}{24}} = 2d \times \frac{24}{d} = 48 \text{ km/h}]

Why isn’t it ((60+40)/2 =50)? Because the car spends more time at the slower speed (40 km/h). For example, if (d=120) km: time to go is 2h, return is3h (total5h), total distance240km. 240/5=48 km/h, which confirms the result.

Answer: 48 km/h.
\boxed{48}

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