Riddle #93

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Question: There is a prison with 100 prisoners, each in separate cells with no form of contact. There is an area in the prison with a single light bulb in it. Each day, the warden picks one of the prisoners at random, even if they have been picked before, and takes them out to the lobby. The prisoner will have the choice to flip the switch if they want. The light bulb starts off.

When a prisoner is taken into the area with the light bulb, he can also say "Every prisoner has been brought to the light bulb." If this is true all prisoners will go free. However, if a prisoner chooses to say this and it's wrong, all the prisoners will be executed. So a prisoner should only say this if he knows it is true for sure.

Before the first day of this process begins, all the prisoners are allowed to get together to discuss a strategy to eventually save themselves.

What strategy could they use to ensure they will go free?

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Riddle Discussion

By: Soraphis on 16/11/15

even if they live forever (not aging, but can be killed) theres no way of ensure they will go free. because the warden picks them by random it is possible (very unlikely but possible) that one person is not chosen at all

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By: whenevertobe on 1/2/15

I don't understand this. If they do this correctly, one day per prisoner, The shortest possible amount of time they can do this in is in 198 days. The chances that the special prisoner will be picked randomly every other day and that every other prisoner will be picked only once (in order for the shortest amount of time to work) is 1 in 1 with 240 zeros after it, in other words, it won't happen. Chances are he will only be picked one out of a hundred times. So chances are that for him to be picked one hundred times is 100 * 100, which is 10,000 days. That's 27 years. Ok, I guess it's possible.

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