Question

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

• A.
• B.
• C.
• D.

Answer 1

The correct option is B

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