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# Circumference and Area of Circles

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##### Description:
1.

Introduce and apply the circumference and area formulas for circles, being sure to discuss units.

2.

Derive Pi () using diameter and circumference.

3.

Demonstrate how to solve for the radius or diameter of a circle given its circumference or area.

4.

Review how to represent the circumference or area of a circle in terms of pi ().

5.

Provide examples that allow for practice calculating the circumference and area of circles.

This packet should help a learner seeking to understand how to calculate the circumference and area of a circle.

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Tutorial

## The Constant Pi

This video explains the concept of pi, including how it is derived.

Source: JasmineWanek on Guaranteach

## The Circumference of a Circle

This video explains how to find the circumference of a circle.

Source: JoeBaxter on Guaranteach

## The Area of a Circle

This video explains how to find the area of a circle and introduces the necessary formula. NOTE: In many cases, it is acceptable to leave your answer in terms of pi (25π, 100π, etc.).

Source: Colleen on Guaranteach

## Expressing Area and Circumference in Terms of Pi

Sometimes, we don't need a numerical estimation of the area or circumerence of a circle. In these cases, it can be easier to express the area or circumference of a circle in terms of pi. To do so, simply don't replace pi with 3.14 (or any other estimation). For example, the area of a circle of radius 3 is

π x r2 = π x 32 = 9π.