 |
 |
My Mail StationeryDear Allstats, A few years back a friend of mine gave me a problem. I don't know if this is the correct place but any insight will be appreciated. Its an interesting and a very difficult one. It goes like this, There are 1000 doors which can take only two states: open or closed. There are 1000 persons. Let us suppose all the doors are closed in the beginning. The first person opens all the doors. The second person changes the state of doors which are multiples of 2. That is the 2nd, 4th, 6th etc doors are closed. The third person changes the state of doors which are multiples of 3. That is if the doors are open, he closes them, if they are closed, he opens them. This process continues that is ith person changes the state of doors which are multiples of i and lastly 1000th person changes the state of the 1000th door. The question is in the end how many doors are open and how many doors are closed? ______________________ Indrajit SenGupta Department Of Statistics St. Xavier's College Calcutta University [log in to unmask] [log in to unmask]