A person covers a certain distance by car at a speed of 30km/h and comes back at a speed of 40 km/h. the average speed during the travel is:

The correct option is 34.3km/h.

To find the average speed of the person for the entire journey, we use the formula for average speed when equal distances are covered at two different speeds.

Let the speed while going be $v_1=30\text{ km/h}$ and the speed while returning be $v_2=40\text{ km/h}$.

When a distance $d$ is covered at speed $v_1$ and the same distance $d$ is covered at speed $v_2$, the average speed is given by the harmonic mean of the two speeds:

$\text{Average Speed}=\frac{2\times v_1\times v_2}{v_1+v_2}$

Substitute the given values into the formula:

$\text{Average Speed}=\frac{2\times 30\times 40}{30+40}$

$\text{Average Speed}=\frac{2400}{70}$

$\text{Average Speed}=\frac{240}{7}\approx 34.2857\text{ km/h}$

Rounding off to one decimal place gives approximately 34.3 km/h.