You need to go from point A to point B, and then back to point A. Points A and B are 20 miles apart. You go to point B at a constant speed of 15 miles per hour. If you want your overall speed to be 30 miles per hour, how fast would you have to go from point B back to point A?
From point A to point B and back again is 40 miles. To cover 40 miles at 30 mph, you must travel that distance in 40/30 hour.
Going from A to B (20 miles) at 15mph will take you (20/15) hour.
40/3020/15= 0
You must travel from B to A at infinite speed.

Posted by Penny
on 20040310 08:49:39 