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21.4 Areas of Circles p. 466. WHAT IS THE AREA OF ONE CIRCULAR RUG? * Remember - area is the number of SQUARE units it takes to cover an area. RECAP : Match the formula with its corresponding shape. PARALLELOGRAMS TRAPEZOIDS RIGHT TRIANGLES “OTHER” TRIANGLES SQUARES RECTANGLES.
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WHAT IS THE AREA OF ONE CIRCULAR RUG?*Remember - area is the number of SQUARE units it takes to cover an area
RECAP: Match the formula with its corresponding shape • PARALLELOGRAMS • TRAPEZOIDS • RIGHT TRIANGLES • “OTHER” TRIANGLES • SQUARES • RECTANGLES • A = lw • A = 1/2 bh • A = s2 • A = bh • A = 1/2 (b1 + b2)
21.4 Areas of Circlesp. 466 • Introduction: • Quick Review • Objective: to learn to use a formula to find the area of a circle • Formula: Area of a Circle A = r Example: Draw a circle with a • 3 inch radius, label it and use the • formula to calculate the area in your • journal 2 Glossary Circle Song
2 • Guided Instruction: • Example 1: use 22/7 for A = r A = A = A = A = A = ft 2
4.6 m 2 2 • Guided Instruction: • Example 2: use 3.14 for A = r A = A = A = m
Check for Understanding: • Group Bag Activity • Objective: Calculate the area of each of your three objects in your bag. Use string and a ruler to accurately measure the radius. Show your work on the recording sheet included in your bag. Raise your hand when finished. Work cooperatively with your group and allow everyone to have a part in measuring and calculating area. Remember: A = r 2