A vehicle travels half the distance with speed v and the remaining distance with speed 2v. Its average speed is:

$\frac{3v}{4}$ $\frac{v}{3}$ $\frac{2v}{3}$ $\frac{4v}{3}$

$\frac{4v}{3}$

$\text{Average speed is } V_{av} = \frac{\text{Total Distance }}{\text{Total Time}} = \frac{2S}{\frac{S}{V} + \frac{S}{2V}} = \frac{2S}{\frac{3S}{2V}} = \frac{4V}{3}$