Question

Abirami has covered some distance with a speed of 20 km/hr in 5 hrs. And then some more distance in another 5 hrs, with a speed of 30 km/hr. Find the average speed for her entire journey.

• A. 50 km/hr
• B. 10 km/hr
• C. 25 km/hr
• D. 30 km/hr

Answer 1

The correct option is C

25 km/hr

Here, since the time of travel is constant, Average speed = $\frac{S1+S2}{2}$ , where S1, S2 ------ given two speeds

That is, $\frac{20+30}{2}=25Km/hr$

So, Average speed = 25 km/hr

Aliter:-

We know that Average speed = $\frac{Totaldistancecovered}{Totaltimetaken}$

ie, Total distance=( 20 km/hr in 5 hrs = 100 km) + (30 km/hr in 5 hrs = 150 km) = 250 km

And, Total time taken = 5 hrs + 5 hrs =10 hrs

So, Average speed = 250/10 = 25 km/hr