Riddle #93

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?

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

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.

Similar Riddles

What month do people sleep the least (easy)

Question: During what month do people sleep the least?

When is 99 more than 100 (hard)

Question: When is 99 more than 100?

Riddle #3363 (medium)

Question: When you're given one, you'll have either two or none?

The Famous Ship Puzzle (medium)

Question: A Japanese ship was sailing in the Pacific Ocean. The Japanese captain of the ship put his diamond chain and Rolex watch on a shelf, went to get a shower and returned ten minutes later. Now listen carefully, as I will only tell it once: When he returned, both the chain and the watch were missing!! He called the crew of his ship together. There were four of them. A British guy was the cook of the ship. The captain asked him: "Where were you the last ten minutes?" And the cook answered "I was in the cold storage room to select the meat for lunch". A Sri Lankan was the house keeping guy. The captain repeated his question to him, and learnt that the Sri Lankan was at the top of the ship correcting the flag which had been put upside down. An Indian guy was the engineer maintaining the ship. Same question, and the Indian told that the he was in the generator room checking the generator. A French guy also served on the house keeping crew. Same question, and the French told that he was sleeping after the night shift. Within ten seconds the smart captain caught the thief. Who was the thief? How did the captain find him? Source: Puzzlevilla

Riddle #3081 (medium)

Question: It is Halloween and your friends dare you to go into a haunted house. You creep up to the door, a little scared wondering what is behind the door. You go in and there is a long hallway leading out into a dark musty room with three doors. You're kind of scared once you are inside. You try to turn back, to get back outside, but when you turn around the door is closed and locked. You yell for help but there is only silence. The room is dark and you look for a light source. You see a light switch and try to turn it on. Sadly the power is out. You are terrified but have no choice but to follow the long hallway to the three doors in the pitch black. Behind one door is a bottomless pit with no end. Behind another door is an electric chair which you must sit in. Behind the last door is a pool full of acid. You must go in one of the rooms to the danger. Which one should you go through?