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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.
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| July 07, 2006 08:25:04 |
#10 |
| deepthi |
Member Since: Visitor Total Comments: N/A |
RE: there are 1000 doors that are of the open-close ty...
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| if doors are one after the other like in a tunnel,667first person closes all the doors.second one closes 2,4,6...third one, to go through opens the door if it was previously not opened. But closes only 3,6,9..999. =>closes 333 doors. And leaves open 664 doors.or0 if they are at the same level. since everybody closes the door they opened. |
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