A car covers first half of its journey with a speed v1 and the next half with a speed v2. The average speed of the car to completes its whole journey is
1
\(\frac{{{v_1} + {v_2}}}{2}\)
2
\(\sqrt {{v_1}{v_2}} \)
3
\(\frac{{{v_1}{v_2}}}{{{v_1} + {v_2}}}\)
4
\(\frac{{{2v_1}{v_2}}}{{{v_1} + {v_2}}}\)