A car covers the first half of the distance between two places at a speed of 40 km/hour and the second half at 60 km/hour. Then the average speed of the car is

Let time taken to cover the first half distance be f , and that for the second half be t₂ suppose the distance between the two stations be x. Then
$\begin{array}{l}{\mathrm{t}}_1=\frac{(\mathrm{x}/2)}{40} \mathrm{and} {\mathrm{t}}_2=\frac{(\mathrm{x}/2)}{60}\\ \therefore \mathrm{t}={\mathrm{t}}_1+{\mathrm{t}}_2=\frac{\mathrm{x}}{80}+\frac{\mathrm{x}}{120}=\frac{\mathrm{x}}{48}\end{array}$
Now, Average speed
$\stackrel{-}{\mathrm{V}}=\frac{\mathrm{X}}{\mathrm{t}}=\frac{\mathrm{X}\times 48}{\mathrm{X}}=48\mathrm{km}/ \mathrm{hour}$