You are travelling to point B from point A at a speed of 30mph. You travel back to point A from Point B (taking the same route) at 60mph. What is your average speed?

The avergae speed is generally total distance/ total time.
But when the distances travelled with the given speeds are equal then the avg speed will  be the Harmonic Mean of the given speeds.

I mean to say if a journey is completed with n speeds say s1,s2,s3,............sn and the distances travelled with these n speeds are equal then the

Avg speed = Harmonic Mean of the n speeds i.e.
Avg speed =  n/(1/s1+1/s2+..........+1/sn)

So coming to this problem

Avg speed is 2/ (1/60+1/30)= 40 mph

Posted by suresh on 2006-10-31 10:28:28