I did not make up this problem.  I didn't even solve it.  But I like it.  So here it is.


23 Prisoners- Problem

23 prisoners are told they will be selected, one-by-one by random drawing, to enter a room in the prison.  In the room are two switches, side by side.  Each switch can be up or down, with no intermediate position.  The switches are not connected to anything.  When the prisoner enters the room he must choose either the right or left switch and change its position - up to down, or down to up.  Then he goes back to his cell.  At any time of the prisoners choosing, any one of them can tell the warden that each and every prisoner has been in the switch room at least once.  If he is right they all go free, if he’s wrong they are all killed – there are no second chances.


What is their PLAN?

Click here for the solution

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