Oh yes, Dd5 does this. I'll take the blame, as I used to use it as a way to test him. I.e., "Mom, what is 25+34?" Then I give an answer off but close to see if he corrects me. But he has turned the tables on me, and now I get that big smirk every time I try to ask him something, accompanied with an outlandish answer. He just finds it hilarious. I think I can tell every time he is doing it..but I have probably ruined him for testing at this age;)