Make some "people" ornaments. For example, you could make a reindeer, a Santa, an elf, a penguin, a snowman and a family consisting of Mom, Dad, brother, sister, baby, dog and cat*. Then, make some cookie ornaments…just a big round circle with chocolate chips. Take one "cookie" and tell your brother, "This cookie is for EVERYone. How will they all get the same amount?" He’ll have to count the "people" and then decide that you need to cut the cookie into 12 equal pieces. Or, start off with twelve cookies and ask him how many everyone gets. Or, 24 cookies and ask how many everyone gets. Once he gets that, take two cookies, and ask him how to divide the cookie so everyone gets the same amount. Set aside the animals (reindeer, penguin, dog and cat) and divide a cookie in fourths. Have him put the cookies back together after they’ve been cut ("three thirds equals one cookie", etc) and tape them back into a whole cookie when you’re ready to hang it on a tree.

*I used these example because 12 is an easy number to divide, as opposed to, like, 9. I also listed different "people", instead of 12 penguins, so it would be easier for a young child to understand and visualize. He can picture in his mind a brother and a sister splitting a cookie for a snack easier than imagining two divided by one.
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