A car moves from $\mathrm{X}$ to $\mathrm{Y}$ with a uniform speed $v_u$. The average speed for this round…
A car moves from $\mathrm{X}$ to $\mathrm{Y}$ with a uniform speed $v_u$. The average speed for this round trip is :
$\sqrt{v_u v_d}$
$\frac{v_d v_u}{v_d+v_v}$
$\frac{v_u+v_d}{2}$
$\frac{2 v_d v_u}{v_d+v_u}$
Solution
Average speed
$\begin{aligned}
& =\frac{\text { Total distance }}{\text { Total time }} \\
& =\frac{2 d}{\frac{d}{V_u}+\frac{d}{V_d}}=\frac{2 V_d V_u}{V_d+V_u}
\end{aligned}$