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 Area of a Circle Part II Unit 2 > Lesson 3 of 6

 Example 1: The radius of a circle is 3 inches. What is the area? Solution: = 3.14 · (3 in) · (3 in) = 3.14 · (9 in2) = 28.26 in2 Example 2: The diameter of a circle is 8 centimeters. What is the area? Solution: 8 cm = 2 · 8 cm ÷ 2 = = 4 cm = 3.14 · (4 cm) · (4 cm) = 50.24 cm2 Example 3: The area of a circle is 78.5 square meters. What is the radius? Solution: 78.5 m2 = 3.14 · · 78.5 m2 ÷ 3.14 = · 25 m2 = · = 5 m

 Summary Given the radius or diameter of a circle, we can find its area. We can also find the radius (and diameter) of a circle given its area. The formulas for the diameter and area of a circle are listed below: or

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