### PROBLEM LINK:

**Author and Editorialist :** Dhruv Mahajan

### DIFFICULTY

Simple

### EXPLANATION:

Average Speed is Not (u+v)/2.

But it is (total distance covered)/(total time taken).

Let distance from A to B is ‘d’, then time taken from A to B is d/u.

And distance between B to A will also remain ‘d’, hence time taken from B to A is d/v.

Total distance covered in the journey is 2d.

Hence average speed will be (total distance covered)/(total time taken),

which is (2d)/(d/u+d/v) which is equal to 2uv/(u+v).

**Remember if u=0 and v=0 then avg speed will also be zero.**