Math teacher mom (and long ago former student of mine), Megan Schmidt sent in the following report for Talking Math with Other People’s Kids month…

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Her husband (who is not a math teacher) and three-year-old daughter—we’ll call her *Marian—*are playing “store”. Marian is trading coins and marbles for books and blankets.

Marian(3 and a half years old): I want to buy a book for mommy to read.

Dad:Pick one and I’ll tell you how much it costs.

M(grabbing a small book from her book shelf): This one is new. Mommy wants to read it to me.

Dad:That one will be 3 silver coins.

M:1, 2, 3. Now I want this one (picks a bigger book)

Dad:How much do you think this one should cost?

M:5 coins!

Dad:How come this one is three (pointing at the small book) and this one is 5? (pointing at the larger book)

M:This book is large, the other is medium.

Megan writes that Marian is quoting Dad here and that Marian’s fondness for the number five may have more to do with her response here than a certainty that five is more than three.

## So what do we learn?

Trading stuff is a fun game to play.

You don’t need all the fancy store equipment. A few coins and a few valued objects (here books) and you’re good to go.

There is so much opportunity to mention, discuss and ask about numbers. Fun, fun, fun.

While the idea that 5 is more than 3 is not at all beyond the grasp of a three-year old, I do love Megan’s tentative attitude here. It certainly is possible that Marian considers five more valuable than any number—that the large book should cost five coins because five is the best number, even if the medium book costs 23 coins.

## Starting the conversation

A beautiful part of this conversation is when Dad asks Marian, *How much do you think this one should cost? *

This question invites Marian to think about and to discuss numbers. It’s lovely, easy to do and is very low risk for both child and parent. It is low risk because there is no wrong answer. Marian is free to set her own price, but *thinking about what that price ought to be* engages her mind in a deeper way than does simply counting out the coins.

Don’t get me wrong: counting out the coins is a lovely activity too. But *How much do you think this one should cost?* is a brilliant conversational move that got even more thinking from a three-year old.