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?

Let the distance between point A and B = d
and the time taken to get back from B to A = t

You are travelling twice as fast on return journey so it will take half the time. Therefore:

d  = 30mph
2t

d = 60mph
t

d = 60t

The average speed = d + d = 2d = 2 x 60t = 40mph
                               2t + t     3t        3t

 

Posted by Lisa on 2006-10-30 07:50:37