Of *course* we do maths! ;-)
Me: Oh! How old are your hands?
Lyddie: My hands are... *pause for dramatic effect* ... 2 years old!
Me: Oh are they? How do you know they're 2 years old?
Lyddie: Because I'm 4, so they must both be 2! Look! 2 *points at one hand*.. and 2 *points at the other hand... is 4! *points at her face*.
Me: Oh! Ok.
I mean, how can you argue with that kind of logic?