- center - middle of circle
- radius - line segment from center to side
- diameter - line segment from side to side through center
- cord - line segment from side to side not through center
- circumference - distance around
When they finished labeling, we used the other side to display measurement of the paper plate. (The plate was just over nine inches; we rounded this number to make it easier for fourth graders to handle.) From the diameter, they were able to calculate the radius, and they were excited because I "let them" use formulas, calculators, and the almighty pi to compute area and circumference. I displayed the formulas, and away they went!
- d = 2r
- C = π d or C = 2 π r
- A = π r 2
Enjoy!
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