conversation with my daughter

One day...

Daughter: Daddy, I will ask you a question. Answer it if you are intelligent.
Father: ok
Daughter: What is 2+1?
Father: 3
Daughter: No. It is 5
Father: How?
Daughter: By mistake

It took us a while to recover. The next day:

Daughter: Mom, i will ask you a question.

Me: ok (i am prepared)

Daughter: What is 2+1?
Me: (aha..) 5
Daughter: Wrong. It is 3
Me: Why? you said 5 yesterday

Daughter: Mistakes don't happen every time

I am speechless.....