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. $\frac{24}{13}$
• B. $\frac{40}{13}$
• C. $3$
• D. $\frac{1}{2}$

Answer 1

The correct option is B

$\frac{40}{13}$

Distance average speed = $\frac{2v_1{v}_2}{v_1+v_2}=\frac{2\times 2.5\times 4}{2.5+4}$
=$\frac{200}{65}=\frac{40}{13}km/hr$