"May I please have one of those biscuits?" asked Alice rather timedly, rather taken aback by the sight of her present company.

"A biscuit?? Oh, I don't know. Those are the March Hare's special un-birthday biscuits, don't you know. Can she have a biscuit, March ?" asked the Hatter.

"A biscuit?? One of mine? Hurmph. Ok, I'm thinking of an integer from one to three (inclusive). If you get it, you can have a biscuit. If not, I'm afraid you'll just have to leave" said the March Hare, leaning back.

"Oh goodness, I don't know" said Alice worriedly. "Couldn't I just get a hint?"

"Oh, all right..." the March Hare sighed. "You get to ask me one yes-or-no question, that's all"

Alice thought for a moment, then smiled, knowing exactly what to ask.

What question should Alice ask?

Alice puts her right hand behind her back.  She asks, "Is the number four less than the number of fingers up on my right hand, or is it a two?"  (This question is asked as a yes-or-no question, not a which-is-it question.)

If the number is 3, the March Hare will say, "No."  If the number is a 2, he will say, "Yes."  If it is a 1, he will say "I don't know."

For those who think that yes-or-no questions must always have yes-or-no answers, take a look at the first question Alice asks: "May I please have one of those biscuits?"  Notice that the Mad Hatter says neither yes nor no!