No  one solved the riddle from two weeks ago (hats), i'm still wating for the answer.

Light bulbs

You are standing in front of a wall with 100 light bulbs and 100 switches numbered 1 to 100.
the light bulbs  are all off, and the switches have the following effect:
flipping a switch will change the state of all the bulbs that are multiples of that switch (so flipping 10 will change the state of 10,20,30,40..100)
you decide to flip the switches one by one, how many light bulbs will be lit at the end?

flipping the first switch(1) will turn all the bulbs on, flipping the second (2) will then turn off all the even numbers etc... finally turning the 100th switch (100) will change the state of the 100th bulb.


enjoy.

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written by hakuu, December 29, 2009

All the bulbs labelled with a squared number (1,4,9...) will be lit since they have an odd number of factors.

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