Four Sisters (Logic puzzle)
There are four identical quadruplets all standing in a line. You can’t tell them apart by anything. Not their clothes, mannerisms, nothing. You do know a few things about them:
- Ava is honest and always tells the truth.
- Becky is also honest, she is however completely delusional.
- Connie is a liar who always tells lies.
- Daisy is a liar and completely delusional.
The sisters want to play a game with you to see if you can identify them.
The game will last four rounds. In each round, you will be able to ask between 1 and 4 yes or no questions.
After the first round of questions, two of the sisters will switch positions. You will not know which ones.
After the second round, the other two sisters will switch positions.
After the third round, three of the sisters will switch positions.
After the fourth round, none of the sisters will switch positions and you have to identify them.
Before each round begins, you will have to decide how many questions you will ask: 1, 2, 3 or 4. You can’t change your mind once you start asking questions and you can only use each set of questions once. (i.e. you can ask 4 questions in round 1 but not again.)
Think you can figure out who is who?
Daisy and Becky
Everything Daisy and Becky know is wrong. They are however, able to understand the questions you ask them and will answer the question that you asked.
If you asked “Is two plus two equal to four?” They will think the answer is no. Since Becky thinks the answer is no, she will honestly tell you “no”, whereas Daisy will lie to you and tell you “yes”. Even though Daisy objectively told the truth, she still tried to lie to you and vice versa for Becky.
The easiest way to think about it is to first answer the question yourself and then turn it to the inverse.