Question

A car is travelled between two villages A and B. Speed of the car while travelling to village B is 100 km/hr and while returning from the village B is 50 km/hr. Find the average speed during the whole journey.

• A. 75 km/hr
• B. $\frac{3}{100}km/hr$
• C. $\frac{200}{3}km/hr$
• D. $100km/hr$

Answer 1

The correct option is C

$\frac{200}{3}km/hr$

We know that average speed = $\frac{\text{Total Distance}}{\text{Total time taken}}$

Let the distance between villages be y.

Now, the time taken to travel from A to B = $\frac{y}{100}$ and from B to A = $\frac{y}{50}$.

Here, distance travelled in both cases is equal.

So, average speed, in this case, will be harmonic mean of speeds = $\frac{2\times 100\times 50}{100+50}$

= $\frac{200}{3}$