We have been working with circles in Geometry the past several weeks and just finished up the standards on finding arc length and area. I didn't want to do worksheet practice, but this is a topic where my kids need a little bit of practice using the formulas. I decided to have them draw their own circles and create sectors within them, then find the arc length and area of the sectors they created. We then extended the activity and I had them 'discover' that circles meet the definition of similar figures since the ratios of corresponding parts are equal. Finally, they worked backwards given specific information about an arc length or sector area to determine the radius or central angle of the sector. I had butcher paper in various places around the room and had them post their circles by class period. This gave them an ok to get up and move, which for some of my boys is necessary. This activity took about 1 1/2 class days (we have 50 minute periods) because we took a few minutes to review how to use the protractor to measure angles. My kids actually did well with the drawing and measuring parts of the activity, which to be honest I was a little concerned about.
Here is the assignment and some pictures of student work.
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| Circles Created by 6th pd |
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| Close up of circles |
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| Similarity Discussion |
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| Working Backwards -- Sample 1 |
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Working Backwards Sample 2
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