rajath_s
 |  Subject: Answer this!!! Wed Apr 29, 2009 2:40 pm | |
| There are 100 doors. There are 100 people.All 100 doors are closed. The 1st person works on the doors which are multiples of 1. the 2nd one works on the doors which are multiples of 2.... Continues till all 100 persons work...
Works means if the door is open it will be closed and vice versa.
After this process is completed state the no. of ddoors closed and opened.With the proof. |
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rajath_s
| | Subject: Re: Answer this!!! Wed Apr 29, 2009 2:43 pm | |
| Answer :
open--> 10
Closed-->90
The opening and closing depends on the no. of factors for a given door no.
Thus there are 10 perfect squares within hundred. So all perfect sqaures have odd no. of factors. so 10 doors are opened.
All numbers which are not perfect squares have even no. of fators. So 90 doors remain closed. |
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