Question

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

• A. 48 km/h
• B. 50 km/h
• C. 52 km/h
• D. 54 km/h

Hint:

For average speed, use \( \frac{2 \cdot s_1 \cdot s_2}{s_1 + s_2} \) for equal distances.

Answer 1

The Correct Option is A

Average speed = \( \frac{\text{Total distance}}{\text{Total time}} \). 
Let distance AB = \( d \). 
Time from A to B = \( \frac{d}{60} \), time from B to A = \( \frac{d}{40} \). 
Total distance = \( 2d \), total time = \( \frac{d}{60} + \frac{d}{40} = \frac{2d + 3d}{120} = \frac{5d}{120} = \frac{d}{24} \). 
Average speed = \( \frac{2d}{\frac{d}{24}} = 2 \times 24 = 48 \) km/h. 
Thus, the answer is 48 km/h.