Find Shapes in Shapes
Lesson 13 of 18
Objective: SWBAT decompose composite shapes into the shapes that they are made up of.
I begin this lesson by reading “Tyrannosaurus Math” by Michelle Markel. This is a fun and engaging book that covers a multitude of math concepts, from addition, to subtraction, measurement and geometry. I like to use it because it keeps the students engaged and can serve as a review of previous concepts taught.
The interrelationships of the shapes in pattern blocks allow children to explore both composing and decomposing of shapes. In this lesson, children build their visualization skills as they work with composite shapes to find the shapes that compose them. To do this, children must identify which shapes were put together to create the composite shape.
Pattern blocks are excellent tools children can use as they analyze composite shapes. Children can place a pattern block directly on a composite shape and turn it, flip it, or slide it to fit part of the composite shape. At first, children may try to fit each pattern block to the composite shape. Then, as they become familiar with the relationships among pattern blocks and learn to identify shapes in composite shapes, children can choose specific pattern blocks and orient the blocks on the page to confirm their answers.
I hand out pattern blocks to students and present the following problem to the class Find Shapes in Shapes.ppt:
Make a new shape with 1 hexagon and 2 triangles. What does your shape look like?
I have children arrange the three pattern blocks to make a new shape and then trace the blocks on a piece of paper. If I notice children struggling to trace, I show children how to hold the pattern blocks so they can be traced, and then I have volunteers share their drawings and compare solutions.
- Did everyone make the same shape? Explain. (No. Some shapes look different because the blocks are arranged in different ways.)
- Does everyone’s shape have the same number of vertices and sides? Explain. (No. Some shapes have more vertices and more sides. The numbers depend on how the blocks are arranged.)
- Suppose you had 1 more triangle. What shape could you make? (a big triangle)
I have found that one of the common misconceptions for students on this standard (1.G.A.2) is that students may not understand that they need to turn the smaller shapes to make the new shape. One way to overcome this is by encouraging students to physically put their pattern blocks on top of the shape on the worksheet. This will help them in moving from the concrete to the abstract stage, by giving them an opportunity to model (MP4) with pattern blocks while visualizing the new composite shape.
I have students look at the model on the top of their Find Shapes in Shapes_worksheet.docx. As we work through the model together, I have children use pattern blocks to build the pictured shape, and I have children trace the line to show the two blocks and trace the circles around the triangle and hexagon.
- Describe how the two blocks are put together. (A side of the triangle touches one side of the hexagon. The triangle points to the right.)
- What do you notice about the sides of the hexagon and the triangle? (They match; they are the same length.)
- Suppose you could use three blocks. Which three blocks could make this shape? (two trapezoids and one triangle)
Once students have successfully modeled the problem on the top of their worksheet, I release them to complete the worksheet.
Here is a sample work from a student who had difficulty in determining which two shapes made the new shape:
To close out the lesson, I have students use 2 pattern blocks to make a new shape. Then I ask them to share their drawing with a shoulder partner and have their shoulder partner draw a line to show what two shapes were used to make the new shape.