Question

A boy walks to his school at a distance of 6 km with constant speed of 2.5 km/hour and walks back with a constant speed of 4 km/hr. His average speed for round trip expressed in km/hour, is

• A. 24/13
• B. 40/13
• C. 3
• D. ½

Answer 1

Answer: (B)

40/13

Answer 2

Distance average speed

$= \frac{2v_{1}v_{2}}{v_{1} + v_{2}} = \frac{2 \times 2.5 \times 4}{2.5 + 4} = \frac{200}{65} = \frac{40}{13}km/hr$