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?

By the problem the respective distance traveled  during the onward journey and the return journey are  equal. Let this distance be s miles..

Also in terms of the tenets comprising the puzzle, it takes respectively s/30 hours and s/60 hours complete the onward journey and the return journey.

Now, the total distance traversed in the course of the entire journey.

= Distance traversed during the onward journey  +   Distance traversed during the return journey

= 2s

Consequently, the required average speed during the course of the journey

= 2s/(s/30 + s/60)

= 40 mph

Edited on October 30, 2006, 8:30 am

Edited on October 30, 2006, 8:42 am

Edited on October 30, 2006, 8:43 am

Edited on October 30, 2006, 11:00 am

Posted by K Sengupta on 2006-10-30 08:29:34