Monday, October 10, 2011

Hands-on Lesson for Area of Circles

This video was created by Karyn Hodgens of Kidnexions.  Karyn gives step by step instructions for having students make targets in order to practice finding area of circles.  I really like the way she incorporates problem solving into the lesson.   She also has some good ideas for demonstrating the concept of subtracting the areas to find the area of the outer rings of the target.

In order to extend this lesson and tie area and circumference into other math standards, you can have students create graphs for the area and circumference of each circle in the target.

Have students: 
  • compare and contrast the 2 graphs
  • describe what types of patterns they see on each graph
  • determine which of the 2 graphs shows a proportional relationship and describe what makes it proportional  (Proportional relationships are linear and they goes through the origin.  They always go through the origin because there is no constant.)
  • use the graphs to make predictions about data points that are not on the graph
  • relate the graphs to the formulas (equations) for area and circumference
  • describe how the equation (formula) and graphs for Circumference are different when you use radius instead of diameter as the independent variable 

If you like this lesson, you might also like Circumference: The Evolution of a Lesson.
What else could you do to extend this lesson for middle school? Leave a comment and share your ideas.

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