• Feb 6th 2007, 05:06 PM
AmandaCLong@aol.com
A cyclist bikes x distance at 10 mph and returns over the same path at 8 mph. What is the cyclist's average rate for the round trip in miles per hour?

(The answer given in the back of the book is 8.9. I don't understand how to get that answer -- my answer was 9)
• Feb 6th 2007, 06:37 PM
ThePerfectHacker
Quote:

Originally Posted by AmandaCLong@aol.com
A cyclist bikes x distance at 10 mph and returns over the same path at 8 mph. What is the cyclist's average rate for the round trip in miles per hour?

(The answer given in the back of the book is 8.9. I don't understand how to get that answer -- my answer was 9)

Just assume the distance is 80 miles.

Then the amount of time for him to got at 10 m/h is 8 hours.

And the amount of time for him to return at 8 m/h is 10 hours.

Average speed is total distance divided by total time.
The total distance was 80+80=160.
The total times was 8+10=18.
The average speed is 160/18=8.8888.. approximately 8.9 hours.

As an excerise show that this is the same number no matter what assumed distance you take in the beginning.