# Tag Archives: Composing and Decomposing

### Tangram Polygons: Composing and Decomposing

In my last post, *Tangrams: A World of Geometry, Part Two*, I talked about the thirteen convex polygon shapes that can be formed with the seven tangram pieces. In the video, I showed how to make five of them, and then I left a challenge for you to look for the remaining eight convex shapes. By way of encouragement, I provided downloads of two of the eight shapes, but left it to you to put the puzzle pieces together to form these two shapes.

In the following video, I review putting together the five shapes. You’ll see that I’ve made the tangram pieces in two different colors. I think it makes it easier to notice patterns and relationships between the shapes and the way the pieces go together to form the shapes.

Now we’ve reviewed putting the five shapes together, and you’ve seen how the colors help us think about the different ways the pieces can be put together. The next video will start by showing those two shapes for which I provided you with downloads in my previous post. Then we follow that up with finding the remaining six shapes. For some of these shapes, there may be multiple ways they can be put together. I don’t claim to have exhausted all of those ways.

Below are several attachments that you can download. The first shows all of the convex polygon shapes that are possible; the second shows one way to put the pieces together to form each shape. Then, there are three pages that have templates for all 13 of the shapes, and finally there are two pages of multiple copies of the tangram pieces in case you want to run them off on two different colors of cardstock.

It is my hope that many of you will find ways to use the tangrams as way to challenge students to look at composing and decomposing shapes. Each of these quadrilaterals, pentagons, and hexagons are composed of the same pieces and so have the same area.

For students in seventh and eighth grade it might be interesting to look at the perimeters of these thirteen shapes. If we took a side of the square tangram piece as the unit of length measure, what would be the lengths of the sides of each of the pieces? Then we could ask about the perimeters of each of the shapes.

Well, maybe that will be a future post.

### Five Squares, One Square: Solution

In two previous blog posts I talked about a puzzle made up of five two by two squares, where each square was cut in two along a line from a vertex to the midpoint of a side. The challenge, which I gave in the first post, was to put the ten pieces together to form… Continue Reading

### Teaching Addition and Subtraction, Part Two

I remember my first experience in a Mathematics Methods Course of a Part/Part Whole Mat. I really liked how the mat could be used for both addition and subtraction. This was the beginning of my pedagogical understanding of composing and decomposing as an addition and subtraction situation. I have already written a series of posts… Continue Reading

### Taking Apart and Putting Together Cubes

In earlier posts I’ve mentioned Friedrich Froebel and his geometric gifts. The third of his geometric gifts was a box containing eight cubes. Instead of the students simply opening the lid and dumping the cubes on the table, he would have the students place the box with the lid down on the table, slide the… Continue Reading

### Five Squares, One Square: Some Hints and an Extension

In an earlier blog post I proposed a puzzle made of five 2 by 2 squares, each of which had been cut along a line from a corner to the midpoint of an opposite side so as to form a right triangle and a trapezoid with two right angles. The challenge of the puzzle was… Continue Reading

### Five Squares, One Square

A while back I posted a five triangle puzzle that involved putting together five 30-60-90 triangles to form a single triangle. Of all of the dozens of puzzles that I own and have made over the years, that is one of my favorites because of the opportunities it provides for students to think about important… Continue Reading

### The Five Triangle Puzzle: Solutions

The Five Triangle Puzzle was the subject of a post back on February 11. I’m hopeful that some of you will have downloaded the pieces and solved the puzzle. The challenge was to put all five pieces together to form a triangle and then to determine if there were other triangles that could be formed… Continue Reading

### The Five Triangle Puzzle: Composing and Decomposing

Beginning in first grade and continuing through the grades, the Common Core Math Standards emphasize composing and decomposing shapes. One way to give students experience with composing shapes is through put-together puzzles. Actually, working at put-together puzzles involves lots of composing and decomposing. Sometimes what we compose is a solution; sometimes it’s not. While the… Continue Reading