1. AREA OF A CIRCLE Lesson 8.05

2. Parts of a Circle

3. Finding the Area Area means the amount of space covered. The symbol is called pi and is approximately equal to 22/7 or 3.141592654 which rounds to 3.14 Diameter = 2 x r Radius = d ÷ 2 A =∙ r 2

4. EXAMPLE Find the area of a circle whose radius is 3 Substitute what you know –A = 3.14 ∙ 3 2 Simplify powers –A = 3.14 ∙ 9 Multiply –A = 28.26

5. EXAMPLE Find the area of a circle whose diameter is 42 m. Find the radius –R = d÷ 2 –R = 42 ÷ 2 –R = 21 Substitute what you know –A = 3.14 ∙ 21 2 Simplify powers –A = 3.14∙441 Multiply –1386 m 2

6. EXAMPLE Find the radius of a circle that has an area of 615.44 square yards. Substitute what you know –615.44 = 3.14 ∙ r 2 Divide –615.44 ÷ 3.14 = r 2 –196 = r 2 Take the square root –R = 14