A car travels half the distance with constant velocity of $40\, kmph$ and the remaining half with a constant velocity of $60 \,kmph$. The average velocity of the car in $kmph$ is

A person goes from point $P$ to point $Q$ covering $1 / 3$ of the distance with speed $10 \,km / h$, the next $1 / 3$ of the distance at $20 \,km / h$ and the last $1 / 3$ of the distance at $60 \,km / h$. The average speed of the person is ............ $km / h$

During the first $18\,min$ of a $60\,min$ trip, a car has an average speed of $11\,m / s$. What should be the average speed for remaining $42\,min$ so that car is having an average speed of $21\,m / s$ for the entire trip?

A person travels along a straight road for the first half time with a velocity ${v_1}$ and the next half time with a velocity ${v_2}$ . The mean velocity $V$ of the man is

A motor cyclist travels a certain distance with a uniform speed of $30\, m/s$ and immediately turns back and returns to starting point with a uniform speed $20\, m/s$. Then the average speed of the motor cycle is ..........$m/s$ :-

A particle moving in a straight line covers half the distance with speed of $3 \,m/s$. The other half of the distance is covered in two equal time intervals with speed of $4.5 \,m/s$ and $7.5 \,m/s$ respectively. The average speed of the particle during this motion is...... $\,m/s$