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        riddles >> hard >> 1000 light bulbs
        
(Message started by: Weasel on Mar 1^st, 2003, 11:47am)

Title: 1000 light bulbs
Post by Weasel on Mar 1^st, 2003, 11:47am

There are 1000 light bulbs all switched off.
Starting with number 1, going up to 1000 by jumps of one
(i.e. 1,2,3, etc.), you will turn ON each light bulb
that is off, and each light bulb that is on will be
turned OFF, then you start again going up this time by
jumps of two (i.e.2, 4,6,etc.) Start all over again with
jumps of 3(i.e.3, 6,9,etc.), jumps of 4,5,6 etc. until
you reach Jumps of 1000. Here is the question: how many
light bulbs will be left on by the time you reach jumps
of 1000? Remember on each jump you will turn ON each
light bulb that is off, and each light bulb that is on
will be turned OFF.

Title: Re: 1000 light bulbs
Post by Icarus on Mar 1^st, 2003, 8:58pm

This is essentially the same puzzle as Circular Jail Cell (http://www.ocf.berkeley.edu/~wwu/riddles/hard.shtml#CircularJailCell), whose thread is here (http://www.ocf.berkeley.edu/~wwu/cgi-bin/yabb/YaBB.cgi?board=riddles_hard;action=display;num=1027864221).

The only substantial difference is 1000 objects rather than 100. There are 31 lights left on at the end.