Answer Detail: RE: there are 1000 doors that are of the open-close ty...

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Question: there are 1000 doors that are of the open-close type. When a person opens the door he closes it and then opens the other. When the first person goes he opens-closes the doors ion the multiples of 1 i.e., he opens and closes all the doors. when the second goes he opens and closes the doors 2, 4 6 8 resly. Similarly when the third one goes he does this for 3 6 9 12 15th doors resly. Find number of doors that are open at last.

March 03, 2006 06:45:59	#3
Diti Rastogi	Member Since: Visitor Total Comments: N/A
RE: there are 1000 doors that are of the open-close ty...
only 31 doors will be left open.... all the numbers which have odd number of factors(the door corresponding to tht) will be left opened. so all the no.s tht are square of some no will ne left open: square of(1,2,3,4,5,6-31)

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