Physics - Kinematics Question with Solution | TestHub

Let the total distance be $2D$. The time taken for the first half is $t_1=\frac{D}{40}$. The time taken for the second half is $t_2=\frac{D}{60}$. Total time$T=t_1+t_2=\frac{D}{40}+\frac{D}{60}=\frac{3D+2D}{120}=\frac{5D}{120}=\frac{D}{24}$. Average speed$=\frac{\text{Total distance}}{\text{Total time}}=\frac{2D}{D/24}=2D\times \frac{24}{D}=48\text{ km/h}$.