My son is in 2nd grade. His math teacher gave the class a quiz, and one question was this:

If a triangle has 3 sides, and a rectangle has 4 sides,

how many sides does a circle have?My first reaction was “0” or “undefined”. But my son wrote “∞” which I think is a reasonable answer. However, it was marked wrong with the comment, “the answer is 1”.

Is there an accepted correct answer in geometry?

edit:I ran into this teacher recently and mentioned this quiz problem. She said she thought my son had written “8.” She didn’t know that a sideways “8” means infinity.

**Answer**

The answer depends on the definition of the word “side.” I think this is a terrible question (edit: *to put on a quiz*) and is the kind of thing that will make children hate math. “Side” is a term that should really be reserved for polygons.

**Attribution***Source : Link , Question Author : Fixee , Answer Author : Qiaochu Yuan*