Question

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

• A. $40$
• B. $45$
• C. $48$
• D. $50$

Answer 1

The correct option is C $48$

Let the total distance be $2D$
For first half distance $D$,
$\text{Time taken}=\frac{\text{Distance}}{\text{Average Speed}}=\frac{D}{v_1}$
For the second half distance $D$,
Time taken = $\frac{D}{v_2}$
For total journey :
$\text{Total distance}=\text{Average speed}\times \text{total time}$
$2D=v_{av}(\frac{D}{v_1}+\frac{D}{v_2})$
$\Rightarrow v_{av}=\frac{2v_1{v}_2}{v_1+v_2}=\frac{2\times 40\times 60}{100}=48kmph$