Math problems

John is pretty good at math. They have just started adding two digit numbers together with regrouping (or carrying over, like how I learned to add). Anyway, he is always impressed with how I can do his math problems in my head. And sometimes he likes to quiz me. "What's 100 plus 100?" I'll answer and he will be amazed and will try to come up with a "harder" question. "What's 200 plus 200?" He cracks me up. This morning he says "What's 10 times 10?" I tell him 100. He grins and says "What's 100 times 100?" I tell him 1,000. He says "I asked a kid on the playground. He said 100. That's easy. But then I asked him what's 100 times 100 and he didn't know. And he was like a fourth grader!" I laughed and said "Your school only goes to third grade." John said "Oh. Well he was a third grader."