A person travels along a straight road for the first half time with a velocity 10m/s and the second half time with a velocity 20m/s . Then the mean velocity is given by

Given that  t1=t2                  v1=10m/st2=t2v2=20m/s∴ The average velocity  =Total displacementTotal time                                       =s1+s2t1+t2=v1t1+v2t2t2+t2=v1+v22=10+202=302=15m/s