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Guest Message by DevFuse

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The clock in the mirror

Best Answer Rainman, 20 February 2014 - 11:35 AM

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#1 bonanova



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Posted 20 February 2014 - 10:07 AM

A while ago, BMAD posted a problem about a clock with indistinguishable hour and minute hands and asked at what times of day, between the hours of noon and midnight, it was impossible to unambiguously determine the time. The hands moved continuously.


This puzzle asks a related question. At what times of day, between the hours of noon and midnight, is it impossible to distinguish the hands of such a clock from those of its mirror image? Clearly noon is one of these times, but not in general thereafter -- since the clock's hands will move clockwise while the hands of its mirror image will move counterclockwise.

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#2 Rainman


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Posted 20 February 2014 - 11:35 AM   Best Answer

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