SOLUTION: Peggy drives to town at a rate of 40 km/h. How fast must she drive BACK in order to average 80 km/h for the entire trip?

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Question 1152453: Peggy drives to town at a rate of 40 km/h. How fast must she drive BACK in order to average 80 km/h for the entire trip?
Found 2 solutions by Alan3354, ikleyn:
Answer by Alan3354(69443) (Show Source):
You can put this solution on YOUR website!
Peggy drives to town at a rate of 40 km/h. How fast must she drive BACK in order to average 80 km/h for the entire trip?
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This is a "trick question."
The time spent going at 40 is the same time as a round trip at 80.
Time is up.
It's not possible.

Answer by ikleyn(52879) (Show Source):
You can put this solution on YOUR website!
.

If one-way distance is "d" kilometers, then one-way time is hours. The two-ways distance ("to there" and back) is 2d, and two-ways time is = hours. In other words, at given condition, all the time is spent for one-way distance "to there", and there is NO TIME for the way back. Therefore, the trip under given condition is IMPOSSIBLE. ANSWER

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Solved, answered and explained. And completed.