Elementary Math, Fractions, Math Talk, Number Sense, Uncategorized

Brownies with Fractions

Any one who knows me personally knows I love to cook and I love math. It’s even better when I combine the two!

Maybe you’re like me and like to have a little bit of fun when you cut your brownies?

My kids know what’s coming when I have one of them come over when I start to cut brownies or bar cookies… a math talk!

As I made each cut in this 8” x 8” pan of brownies my son and I had a conversation. Let me walk you through the questions I asked him. When I do this with students in my class, they each have a few post-it notes to try this out conceptually.

Let’s start by cutting this into halves. How many equal parts should be make to be halves? Show me which way you would like me to cut them to make halves.
Great! So we have halves. What happens if we can each of these halves in half? How should we cut each of them in half?
Here’s where I had my son close his eyes and when he opened them I had the brownies cut like this. I asked him, “Are these the same size? What are the parts?” Me cutting the brownies like this made his brain go bonkers, but as we talked it through he came to find that each of these parts were equal and fourths.
My son got on board and helped me decide how we cut each of the fourths in half. Before we did the actual cut, he had to predict how many parts there would be. I was trying to get him to see the pattern. *This is the point in which my class of 4th graders were confused that the triangles on the right side were congruent to the rectangles on the left. I had to go back and picture in class and draw on the board cutting the fourths in half.
We then made horizontal cuts in the brownies and talked about which pieces were congruent and which were not. More importantly, we talked about WHY the pieces weren’t congruent. My son said we needed another cut..
L made additional diagonal cuts on the right to create these different sized triangles. This gave us the opportunity to talk about congruent parts of the brownies. The squares on the left have the same area as the larger triangles on the right, but it takes 2 of the smaller triangles on the right to equal the left. It was a great discussion in class as well.

I have provided you with a handful of images below that I have used in my own classroom to have math talks with my students. Sometimes I put up an image and give them a few minutes to jot down notes and chat with their group about what math they see and other times I pose questions to them. Either way, it’s an easy and fun way for students to engage with math in the real world.

Please help yourself to the free downloads below of food fraction pictures you can use in your classroom.

Baked potato casserole

Part of a Cheesecake

Part of a Cheesecake 2

Taco Dip

Chocolate Pie

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