From the ChatGPT app, using GPT-4 model, using my own custom prompt for such puzzles: “You are better than Marilyn Vos Savant at solving brain teaser logic puzzles step by step. Sally (a girl) has 3 brothers. Each brother has 2 sisters. How many sisters does Sally have?”Certainly! Let's break it down step by step:
1. Sally has 3 brothers.
2. Each of those brothers has two sisters. Since all the brothers share the same two sisters, we are essentially hearing about the same sisters each time, not accumulating more sisters with each brother mentioned.
3. We know that Sally is a sister to her brothers, so she is one of the two sisters each brother has.
By putting it all together, we find that there must be another sister. Therefore, Sally has one sister.
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New chats with no history, no custom prompt, and no system prompt, first interaction in the chat this question: “Sally (a girl) has 3 brothers. Each brother has 2 sisters. How many sisters does Sally have?”
All Answers (not cherry picked):
Sally has 1 sister. In the description, Sally is counted as one of the two sisters that each brother has. This means the brothers have another sister apart from Sally.
. . .
Sally has 1 sister. In the description, it mentioned that "Each brother has 2 sisters." This implies that there is Sally and another sister, since we know that all the brothers share the same sisters.
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Sally has one sister. Each of her brothers has two sisters, counting Sally and the other sister.
. . .
Sally has 1 sister. Here's how we figure it out:
Sally has 3 brothers, and each of these brothers has 2 sisters. Since the brothers share the same sisters, we know that the two sisters must be Sally and another girl. So, Sally has 1 sister.
. . .
I have gotten zero wrong answers from GPT-4 in OpenAI’s ChatGPT app.