If a car covers 2/5th of the total distance with v1 speed and 3/5th of the total distance with v2 then average speed is

$v_{a v g} = \frac{s_{1} + s_{2}}{t_{1} + t_{2}}$

$v_{a v g} = \frac{s_{1} + s_{2}}{\frac{s_{1}}{v_{1}} + \frac{s_{2}}{v_{2}}}$

$v_{a v g} = \frac{\frac{2 s}{5} + \frac{3 s}{5}}{\frac{2 s}{5 v_{1}} + \frac{3 s}{5 v_{2}}} = \frac{5 v_{1} v_{2}}{2 v_{2} + 3 v_{1}}$

If a car covers 2/5th of the total distance with $v_{1}$ speed and 3/5th of the total distance with $v_{2}$ then average speed is