A body goes from point X to point Y with a speed of 10 m s-1. It comes back to X with a speed of 20 m s-1. The average speed of the body during the journey is ______.
A15 m s-1
B16.6 m s-1
C13.3 m s-1
D30 m s-1
Hi, I am a bit confused about this question... How could the answer possibly be 'C'? The answer is most obviously A... Please comment.