# What's my number? [duplicate]

I am thinking of an integer $1,2$ or $3$. You can ask me only a single question to which I can reply "Yes", "No" or "I don't know". I will be completely honest. What will you ask me to figure out what number I am thinking about?

Note: Since there are an infinite number of solutions to this puzzle, I'll select the wittiest one / the one with most upvotes. (Because the one I came up with is kind of overly mathematical and a little too out of the box.)

• The possible duplicate, though very similar, has 4 possible answers ("maybe"), which in essence changes the answers.
– AvZ
Commented Feb 8, 2015 at 14:58
• "Maybe" can be changed to "I don't know" in almost all circumstances. Besides, there are enough answers on the other question that don't use "maybe" already. Commented Feb 8, 2015 at 15:03
• @AvZ I have a feeling this question is gonna be closed, perhaps you should accept my answer, and tag this as open-ended. Commented Feb 8, 2015 at 15:06
• @warspyking Like I have said before, comments like that make me think you answer for the reputation only. Commented Feb 8, 2015 at 23:41
• @mdc32 My answer was the only understandable one here. Why just leave it unanswered? Commented Feb 9, 2015 at 0:53

I'm going to think of a random number too, 1 or 2. If we multiply our numbers, will the product be greater than or equal to 3?

• No -> 1
• Yes -> 3
• I don't know -> 2
• Nice, this works. Let's see what others think. I am going to acxept this within a day or 2 if there aren't any other better answers.
– AvZ
Commented Feb 8, 2015 at 14:55
• @AvZ If there is a better answer I'll just have to get cleverer. Commented Feb 8, 2015 at 14:56
• Is there any particular reason why people downvote "duplicatish" posts.
– AvZ
Commented Feb 8, 2015 at 17:44
• @AvZ Yes, because you didn't research enough. Commented Feb 8, 2015 at 19:08

I'm thinking of either 1.5 or 2.5 . Is your number greater than mine?

• Yes - 3
• No - 1
• I don't know - 2

Is either of the following true:

• Your number is $$1$$.
• Your number is $$2$$, and the Riemann hypothesis is true?

If you say "yes", it's 1, if you say "I don't know", it's $$2$$, and if you say "no", it's $$3$$. And, if you say "yes" and I find out your number isn't $$1$$, I'm gonna want a proof.

(You could replace "Riemann hypothesis" by anything else the answerer would not know. For instance, "Is a random number I just thought of equal to $$1$$?")

• If the number is 1, the answer is YES (as $\frac{1}{2-1}>0$ )
• If the number is 2, the answer is I DON'T KNOW (as $\frac{1}{2-2}$ is undefined )
• If the number is 3, the answer is NO (as $\frac{1}{2-3}<0$ )
• You generally consider the form $\frac{1}{0}=+\infty$ which is greater than $0$
• @AvZ I would consider $\frac{1}{0} = \pm\infty$, but the other answers are better anyway. Commented Feb 8, 2015 at 17:37