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Big Ideas:
We can find the diameter of a circle by using the formula diameter = 2 x radius.
We can find the radius of a circle by using the formula radius = diameter / 2.
This lesson introduces the diameter and radius of a circle. In the lesson students are asked to investigate a problem for the Pizza Pi Palace, a local pizzeria that offers pizza in four different sizes. Pizza Pi Palace wants to describe the size of their pizzas based on the radius and diameter. Students are asked to calculate the radius and diameter of the small, medium, large, and family sized circular pizza pies. By solving for both radius and diameter, students will explore how the diameter and radius are related, allowing them to explore the conceptual understanding of the formulas r = d/2 and d = 2r. The mathematical concepts in this lesson lay the foundation for the subsequent development of the area and circumference formulas.
Vocabulary: radius, diameter
Special Materials:
Rulers (optional)
Protractor (optional)
Paper (isometric or graph)