A certain town has 100 married couples (husband and wife only). Everyone in the town lives by the following rule:
One day an outsider came to the town and some how, got to know about all the cheating and non-cheating husbands.
The next day while leaving he announced to the entire town – “There is at least one cheating husband in the town”.
What will happen ?
Solution:
This problem is in the lines of Blue eyed Islander Puzzle. The solution to the problem is also in the lines of this puzzle only. Let’s start methodologically and consider cases:
If there is only 1 cheating husband
99 women knows who is cheating. Only 1 woman (wife of the cheater) does not know of anyone cheating. Wife of the cheater must be thinking that none of the husbands cheat. After announcement, she will realize that her own husband is cheating (if anyone else is cheating, then she must have been aware of it).
So the cheating husband will die on the first day (same day).
If there are 2 cheating husbands
Wives of both the cheating husbands, think that there is only one cheating husband (i.e the other one) and hence will expect the other husband to die on the first day. When no one dies on the first day, then on the 2’nd day both of them will realize that their husband is also cheating (along with the other one).
Hence, both the cheating husbands die on the 2’nd day.
If there are n cheating husbands.
Going by the above logic, All the n cheating husbands will dies on the n’th day.
2 Comments
Well explained. Thank you very much.
Interesting. If this were asked to me during an interview, I would point out that the question was flawed. The “immediately killed” part doesn’t work. In order for the answer to make sense, you need a daily cadence to be part of the question. So it should have said something like “the husband will be killed at midnight the night the wife finds out.”