Question

A man covers the first half of the journey at the speed of 60 km/h and the remaining at the speed of 84 km/h. What is his average speed (in km/h)?

• A. 70
• B. 60
• C. 65
• D. 75

Answer 1

Answer:

A. 70

Since the journey is divided into equal distances, we use the harmonic mean formula for average speed:

$\text{Average speed} = \frac{2ab}{a+b}$

$v_{avg} = \frac{2ab}{a+b}$

Here, (a = 60), (b = 84)

$v_{avg} = \frac{2 \times 60 \times 84}{60 + 84}$

$= \frac{10080}{144} = 70$

Final Answer:

70 km/h