A man starts walking north at 4 ft/s from a point P. Five minutes later a woman starts walking south at 5 ft/s from a point 500 ft due east of P. At what rate are the people moving apart 15 minutes after the woman starts walking? (Round your answer to two decimal places.)
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$\begingroup$ There’s no unique solution if all that happens a few meters away from the South Pole. $\endgroup$– Michael HoppeMay 5, 2018 at 19:00
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1 Answer
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The method is basically sound with one error. In your figure, you have a right triangle with leg lengths $500$ and $4800+4500$. The length of the hypotenuse of that triangle is $\sqrt{(4800+4500)^2 + 500^2}$, not $\sqrt{4800^2 + 4500^2 + 500^2}$.
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$\begingroup$ I get something between $8.98$ and $8.99$ that rounds up. Anyway, this is a lot more reasonable than $12.68$. After all the fastest they could walk away from each other is $9$ ft/s, and that's only if they are walking directly away along the same line. $\endgroup$– David KMar 16, 2015 at 13:30
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$\begingroup$ As I said, the answer rounds up in this case. $\endgroup$– David KMar 16, 2015 at 14:30