A person travels along a straight road for half of the distance with a velocity 30km/h and the remaining half distance with a velocity 50km/h. Then the average velocity is given by

Given that    s1=s2 s2=S2                     v1=30 km/h                     v2=50 km/h∴ Time taken to cover first half of the distance  t1=s2v1The time taken to cover second half of the distance  t2=s2v2Average velocity  V¯=Total dispalcementTotal time                                  =S1+s2t1+t2=s2+s2s2v1+s2v2=2v1v2v1+v2=2×30×5030+50=2×30×5080=3008=1504=37.5km/h