A body covers half a distance with a speed of 20m/s and the other half with a speed of 30m/s.Find the average speed of the whole journey?

25m/s

Deepak, consider a test piece of road. A good length of road to choose would be one that is easily divisible by both your speeds, like 120m.

So he travels 60m at 20m/s and 60m at 30m/s

What is the total time he takes? What is the total distance? Therefore what's his average speed?

Let me know if you have any trouble.

Ah thanks for the explanation, see where my "expert" guess falls down!