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Area of a circle

Area of a circle. Lesson 4.5 February 12 th , 2012. It’s quiz time!!!. #1 What is the formula for finding the area of a triangle?. #2 What is the relationship between parallelograms and triangles?. #3 What is the area of the triangles?. 6 cm. 6 cm. #4 What does congruent mean?. #5.

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Area of a circle

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  1. Area of a circle Lesson 4.5 February 12th, 2012

  2. It’s quiz time!!! • #1 • What is the formula for finding the area of a triangle?

  3. #2 • What is the relationship between parallelograms and triangles?

  4. #3 • What is the area of the triangles? 6 cm 6 cm

  5. #4 • What does congruent mean?

  6. #5 • Find the area of a triangle with a base of 7 and a height of 4.

  7. #6 • Find the area of this triangle. 5.1 cm 7.2 cm

  8. #7 • Find the area of the triangles. 1 cm 3 cm 3 cm 1 cm 7 cm

  9. #8 • What is the diameter of this circle? 5.4 mm

  10. #9 • What is the area of this parallelogram? 14 m 20.2 m

  11. #10 • What is the circumference of a circle with a radius of 3.6 ft?

  12. b x h ÷ 2

  13. #2 • There are two congruent triangles in one parallelogram. • OR • A parallelogram divided in two equals two congruent triangles.

  14. #3 • Area of parallelogram A = b x h A = 6 x 6 A = 12 cm Area of triangles A = 12 ÷ 2 A = 6 cm

  15. #4 • Two shapes that are EXACTLY the same, but, they are not in the same orientation. • OR • Two shapes that are the same, but facing a different way.

  16. #5 • A = b x h ÷ 2 • A = 7 x 4 = 28 • 28 ÷ 2 = • A = 14 cm

  17. #6 • A = b x h ÷ 2 • A = 7.2 x 5.1 ÷ 2 • A = 18.36 cm

  18. #7 • 1 x 3 = 3 ÷ 2 • 1.5 cm

  19. #8 • D = 5.4 x 2 • D = 10.8 mm

  20. A = b x h • A = 20.2 x 14 = 282.8 m • A = 282.8 m

  21. C = 2Лr • C = 2 x 3.14 x 3.6 • C = 22.6 ft

  22. Toilet paper tube... • If I cut a circle in half...I get a rectangle! • Each of the shorter sides of the rectangle would be equal to the radius. • The sum of the two longer sides is equal to one half the circle’s circumference.

  23. Area of a rectangle = b x h Height = r Base = Лr

  24. Therefore, • The area of the rectangle is Лr x r = • Лr squared. • So, the formula for finding the area of a circle is A = Лr squared. You can use this formula anytime you know the radius.

  25. Find the area of this circle.

  26. Find the area of this circle.

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