# What Could This Be? A Partial Shapes Book

What language might children who haven’t learned about right angles use to describe the angles in a rectangle and square?

Tracy Zager had some lovely things to say about how children will use examples and gestures to communicate their meaning.

Then I got to thinking about how young children may not have had many opportunities to think about the size of each angle in a rectangle.

Informally, kids will have heard a lot about how a rectangle has “four angles the same size” but if you know that, you don’t necessarily know that any particular size is necessary. Could it be four small angles, or four large angles?

I wanted to design something that would allow children to explore their ideas about that. So I started sketching out some ideas, and the result is a very early draft of a new book.

Imagine you are looking through a circular hole, and you see the blue region that is printed on the next page. What could that blue shape be? Could it be a rectangle? Does it have to be?

In order to answer those questions, it’s going to be useful to think about the angles and the side lengths of shapes you see in your head.

Ideally, a published version of this book will have a whiteboard page with a hole and come with a dry-erase marker so you can sketch your ideas before you turn the page and see a collection of shapes it could be.

For now though, you’ll just want to print the book out, sit down with a child and a pencil and have some fun talking shapes. As always, feedback welcome. Find me on Twitter, or send a note through the Contact page on this blog.

If you like books in development, you should know about Is It or Not? Vehicles, a joyful adventure in mathematical definitions—fun for all ages!

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