Three prisoners in deathrow are put together. They each get a unique number on their forehead. They are NOT allowed to speak to each other, only to their guard. They only get 2 clues:
- The number on their head is always higher than zero
- One of the numbers is the total of the other two numbers.
If they can guess their numbers, they are free to go.
- Person 1 gets asked if he knows his number. He says he doesn't.
- Person 2 gets asked the same, but also replies that he doesn't know
- Person 3 is being asked but doesn't know either.
Since none of them answered wrong. They get another chance.
- Person 1 again doesn't know.
- Person 2 also doesn't know.
- Person 3 however does know the answer this time: It's 148 on his head. This answer is correct and he is allowed to leave.
Question: What are the numbers on the heads of person 1 and 2 and how does person 3 know his own number?
Prisoner 3 sees the other two have both the same number on their head - which is 74 but Prisoners 1 & 2 only see number 148 and 74 on the other two prisoners heads respectively. So they cannot really tell if they have to subtract or add to get their own number.
Harder hats on deathrow version
in New Logic/Math Puzzles
Posted
Prisoner 3 sees the other two have both the same number on their head - which is 74 but Prisoners 1 & 2 only see number 148 and 74 on the other two prisoners heads respectively. So they cannot really tell if they have to subtract or add to get their own number.
Correct?