[#TMWYK] Logic & Equivalence

Some logic and equivalence #tmwyk* this morning:

8yo (trying to get me to do something for her): Please plus please!
Me: What does that mean?
8yo: It means yes.
Me: So, what does a thank you + thank you mean?
8yo: That means yes, too.
Me: How about a no thank you plus a thank you?
8yo: No.
Me: And a no thank you plus a no thank you?
8yo: Maybe.
Me: How does that work?
8yo: Because there are two no's and two thank you's.
Me: You mean there's an equal number of both?
8yo: Yeah.

A little later, about our cats Max and Lucy:

8yo: Max + Lucy = Trouble
Me: That's for sure.
8yo: Actually, cat + cat = Trouble.
Me: So, Max + Lucy = Cat + Cat = Trouble!
8yo: NO!
Me: Why not? If cat + cat is trouble, and so are Max + Lucy, then don't Max + Lucy = cat + cat? They both equal trouble...

She had reached her limit with my questions by then, but I found the whole series of ideas rather fascinating.  First because this was the first time I've had this particular kind of conversation with her. It seems Christopher Danielson's Talking Math with Your Kids is really having a positive influence on my conversational abilities! Second because the whole idea of equivalence in equation form seems to flummox kids. The equal sign often seems to mean "an answer" and not a relationship. It was fun to test/push her a little on this idea and see how it would play out in conversation.

*#tmywk is the hashtag for Talking Math with Your Kids on Twitter. You can also go to Talking Math with Your Kids.  You'll be glad you did!!