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Heather's Bikini
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Heather is such a fast swimmer, she is banned both from women's and men's races for unfair competition. Even when she goes for a leisurely swim, which she does every day, both in winter, spring, summer, and autumn, in her gorgeous white string bikini, she swims at a whopping 5 miles per hour in still water.
Today Heather swam in a river that flowed at 4 miles per hour. So, when she swam with the current, she went 9 miles per hour, and when she swam against the current, she only went 1 mile per hour.
While she was swimming the freestyle against the current, she lost her bikini top and didn't notice. When she was exactly 5 miles away from her top, she decided to start swimming the backstroke, but realized she had lost her top when she heard someone say something that I cannot mention because this is supposed to be a family-friendly site.
At this point Heather immediately turned around and swam towards her top. Despite being in such a hurry, she applied the same force as before, knowing the current would help her.
If Heather lost her top exactly at noon, and her speed did not change regardless of whether she was wearing it, when did she catch up to her top?
Today Heather swam in a river that flowed at 4 miles per hour. So, when she swam with the current, she went 9 miles per hour, and when she swam against the current, she only went 1 mile per hour.
While she was swimming the freestyle against the current, she lost her bikini top and didn't notice. When she was exactly 5 miles away from her top, she decided to start swimming the backstroke, but realized she had lost her top when she heard someone say something that I cannot mention because this is supposed to be a family-friendly site.
At this point Heather immediately turned around and swam towards her top. Despite being in such a hurry, she applied the same force as before, knowing the current would help her.
If Heather lost her top exactly at noon, and her speed did not change regardless of whether she was wearing it, when did she catch up to her top?
Answer
Heather caught up to her bikini top at exactly 2:00.The current of the river is irrelevant. The distance between Heather and her top will always either increase or decrease at exactly 5 miles per hour. When Heather's speed against the current is added to the speed of the current (that is, that of her top), or when the speed of the current is subtracted from Heather's speed with the current, the result is always Heather's speed in still water.
Since Heather was 5 miles away from her top, it obviously took her 1 hour to realize it was gone. Then it took her 1 hour more to get it back. Add these 2 hours to noon to get 2:00 PM.
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