Reflection: Intrinsic Motivation Little Bears Vest - A lesson on Symmetry - Section 1: Warm Up


This warm up proved to be so fun and led to GREAT class discussion.  I had intended to really review fractional parts of shapes in order for students to find the fractional monetary amount of each shape, but the discussion ended up being way more than that! 

Immediatly after the video, a student said something like "yeah, like a circle has 360 lines of symmetry because it has 360 degrees." Another student then responded and said, "acutally it would be more like 180 lines of symmetry because of the half circle."  Several more students added to the conversation, either agreeing with the intial statement or the 180 degree statement. At this point, I put a part of a protractor under the document camera and zoomed in very large. Then I simply asked, "do you think it's possible there are lines of symmetry between the one degree marks?"

Then, what happened was amazing. My students became a buzz of talking and thinking. It was so exciting to see them.  They did not come to the conclusion that there are in fact infinite lines of symmetry, but they were very close.  I was SO proud of them and thought about how far they've come in their mathematical thinking and communication since the beginning of their fourth grade year. 

The conversation gave students a chance to reason about lines of symmetry and begin to discover that a circle has an an infinite number of lines of symmetry. Even though the concept of an infinite number of lines is fairly abstract, fourth graders can understand infinity in an informal way. Just as there is always a fraction between any two fractions on the number line, there is always another line through the center of the circle "between" any two lines through the center of the circle. So if you identify a certain number of lines, you can argue that there is always at least one more.

You hear more thoughts in my reflection video.


  How many lines of symmetry in a circle?
  Intrinsic Motivation: How many lines of symmetry in a circle?
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Little Bears Vest - A lesson on Symmetry

Unit 9: Geometry
Lesson 11 of 11

Objective: SWBAT identify lines of symmetry and solve problems involving money and fractional parts of shapes.

Big Idea: In this partner work lesson, student work with pattern blocks and their creativity to design a shape pattern that has at least one line of symmetry. Students also find the fractional value of each shape and calculate in order to calculate the total value

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4 teachers like this lesson
Math, Symmetry, Money, problem solving, addition, subtraction, multiplication, inquiry, fractional parts, hands on
  67 minutes
little bear vest
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