When I teach angles or the properties of circles, I find that most children have difficulty cutting out a true circle (even with a blackline). I have resorted to purchasing cheap coffee filters (not the cone shaped ones) and ironing them flat. You can iron several filters at one time, and once they are ironed, they form excellent ready-made circles. Here are some of the ways you can teach angles using these circles.
- Introduce the fact that each and every circle contains 360 degrees.
- Have the students fold their coffee filter in half. Discuss that this is a straight angle. Ask, “How many degrees does it contain if it is one-half of a circle?” (180 degrees)
- Have the students fold the coffee filter one more time, into fourths. Talk about this angle being called a right angle and that it contains 90 degrees. Ask, "What fractional part of a circle is this?"
- Have the students use this fourth of a circle to locate places in the classroom where it will fit (e.g. the corner of their desk, a corner of a book, a corner of the board).
- Explain that these corners are right angles and without right angles, we would live in a crooked world. Nothing would be straight!
- With older students, have them write the parts of the circle and the formulas needed for solving problems about circles on the coffee filter circle.
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| Writing Formulas on the Coffee Filter Circle |
Linking Math and Literature for Older Students
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