Combine 2D Shapes

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SWBAT use objects to compose new two-dimensional shapes.

Big Idea

Shapes, shapes, shapes! What new interesting shapes can you make when you combine 2D shapes? In this lesson students will compose new 2D shapes from multiple shapes.

Activating Strategy

10 minutes

I start the lesson by reading “Shapes, Shapes, Shapes”.  This book is a wordless book with great pictures.  I like to use this to engage the students in finding various shapes throughout the book. You can make a game out of it, sort of like I Spy, and really get them revved up for this lesson.

After we look through the book, I draw a word web with four spokes and write “Two-Dimensional Shapes” in the center (Combine 2D Shapes_student web.ppt). I draw a circle, square, rectangle and triangle at the end of each spoke. I then have a student write the name of everyday objects that resemble each shape in the web.

I ask students to tell me real objects that belong in each category. In this video, the student is explaining her reason for putting a sun in the circle of the shape web:

Then I let students use pattern blocks to create composite shapes. I have found that an effective way to teach math lessons that introduce the ideas of informal geometry is to let children explore and experiment. In addition to the explorations in composing shapes presented in this lesson, encourage children to find other ways to use the triangles and rhombuses to build trapezoids and hexagons and to use the pattern blocks to make other shapes. I do this by allowing them to play with and explore making shapes pattern blocks for a few minutes before beginning the lesson.

As children investigate ways to combine the pattern blocks to make other shapes, I have children record what they learn and look for relationships among the shapes. If children do not know the name for the rhombus, I tell them use the color name to refer to the shape. Some may discover relationships among the pattern blocks. For example, a hexagon may be composed with 6 green triangles, 3 blue rhombuses, or 2 red trapezoids, or with a combination, such as 2 rhombuses and 2 triangles. Activities that focus on relationships also help build problem-solving skills.

In the standard 1.G.1.2, some students may be unable to visualize how to combine the smaller blocks into the larger shape.  To support them, I have children place a rhombus block over part of a hexagon and move it around until it matches one part of the hexagon. I then have them continue adding rhombuses until the hexagon is covered.  By having the students put the shape on top of the composite shape, it will help them to visualize and compose the new shape.  By allowing students to manipulate pattern blocks, they are learning to experiment with using models in math (MP4).

Teaching Strategies

15 minutes

I show students pattern blocks and name the shapes and read the following problem to the class (it is also on the first slide of the Combine 2D Shapes.ppt):

Karen has some pattern blocks. She puts two triangles together. What is a new shape Karen could make.

  • What is the color of the triangle pattern block?  (green)
  • How many triangles does Karen put together? (2)

I then have children use two triangle pattern blocks to form a shape and ask children trace the triangles to record their new shape. I have volunteers share their drawings with the class.

  • How are your drawings the same? They all use two triangles.
  • How are your drawings different? Children will likely observe that their drawings show different ways to put the triangles together.

As I work through the model on the second slide of the powerpoint with the class, I like to have children use two trapezoid pattern blocks to model the hexagon as shown.

  • How can you describe the way you put the trapezoids together? (The long sides go together.)
  • What do you notice about the sides and vertices? (A trapezoid has 4 sides and 4 vertices. When I put two trapezoids together to make a hexagon, the hexagon has 6 sides and 6 vertices.)

Independent Practice

30 minutes

Before beginning questions 1 and 2 on the worksheet, encourage children to turn the blocks over and around to help visualize the shape they need to make.  I also have those struggling students select the new shape and place it on their desk.  I then show them how to select the shapes needed and place them on top of the new shape, turning it as needed so that the new shape fits.

I then allow students to continue the Combine 2D Shapes_worksheet.docx independently as needed.


5 minutes

To close out this lesson, I have students draw to show what shapes they would use to make a rectangle.