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        riddles >> easy >> Mirrored clock
        
(Message started by: maryl on May 30^th, 2003, 4:27pm)

Title: Mirrored clock
Post by maryl on May 30^th, 2003, 4:27pm

A boy leaves home in the morning to go to school. At the moment he leaves the house he looks at the clock in the mirror. The clock has no number indication and for this reason the boy makes a mistake in interpreting the time (mirror-image). Just assuming the clock must be out of order, the boy cycles to school, where he arrives after twenty minutes. At that moment the clock at school shows a time that is two and a half hours later than the time that the boy saw on the clock at home.

The Question: At what time did he reach school?

Title: Re: Mirrored clock
Post by jabhiji on May 30^th, 2003, 7:26pm

Nice puzzle, Maryl. The boy reaches school at [hide] 1:25 [/hide]. A perfect excuse for missing a couple of classes. He would say "[hide] I swear it was 10:55 when I started....[/hide]".

Title: Re: Mirrored clock
Post by RichardBerger on May 30^th, 2003, 9:43pm

Hmmm.... I haven't looked at the answer above but shouldn't there be four answers due to symmetry? [hide]The first should be at that boy read the clock as 10:55AM, but it was actually 1:05PM, so that when he arrived at school at 1:25PM, it was 2.5 hours after the time he saw on the clock this is based on the thinking that the hands of a clock overlap every 1:05 5/11 and 1:05 is 5/11 shy of an overlap, which is symmetric with 10:55 which is 5/11 after the overlap at 10:54 6/11. Of course, there is now the obvious "other answer" of 10:55PM and 1:05AM (night school?). But isn't there another symmetry at the bottom of the clock - at 5:25PM/7:35PM? I guess if I weren't so tired from trying to solve the "A Good Beginning" puzzle, I would work this out [/hide]. Thanks Maryl for another brain twister - I had to run around to find an analog clock - and unable to find one, realized I could make do with the one in my system tray.

Title: Re: Mirrored clock
Post by RichardBerger on May 30^th, 2003, 9:52pm

Nope, I was confused. The symmetry I was thinking about is not valid. Only one answer (and its trivial AM/PM swap).

Title: Re: Mirrored clock
Post by redPEPPER on May 31^st, 2003, 8:26am

And how about [hide]he arrives at school at 7:25 AM? The riddle says he leaves for school in the morning. So it's either that or it's 1:25 ... AM! Poor guy...[/hide]