We are working our way through Singapore's Challenging Word Problems 1. We just got to the section on multiplication. We haven't worked on multiplication since we covered it in Primary Math 1B which was around Christmas.
So here's how two of our problems went this morning:
D-Man: That's 9x2. I have to go potty. Be right back.
D-Man: (Immediately after the quick trip to the restroom) That's 18.
Mom: That was fast, how did you know that?
D-Man: Well, I was thinking about it while I was going potty. 5-2's is 10 and another 4-2's is 8. 10 plus 8 is 18. It's really just an adding problem.
Mom: Wow, that's exactly right.
D-Man: (After reading the probem) That's 3x2. Hmmm...That's 10-4. It's 6.
Evidently, he thought that 5x2 = 10 and 2x2 = 4. When you subtract them, you get 3x2.
Interesting math day.