1. Slide 1 11-2 Areas of Polygons and Circles  Areas on a Geoboard  Converting Units of Area  Land Measure  Area of a Rectangle  Area of a Parallelogram

2. Slide 2 11-2 Areas of Polygons and Circles  Area of a Trapezoid  Area of a Regular Polygon  Area of a Circle  Area of a Sector

3. Slide 3 Areas on a Geoboard Addition method – divide an area into smaller pieces and then add the areas. What is the area of this figure? 19 square units

4. Slide 4 Rectangle method – construct a rectangle surrounding the entire figure and then subtract the areas of the regions a, b, c, d, and e.  Area = 16 – (3 + 1 + 1 + 1 + 1) = 9

5. Slide 5 Now Try This 11-5Page 752 How many of each of the following nonstandard shapes are contained in the figure 11-15 Triangle 12 Rhombuses 6 Trapezoids 4

6. Slide 6 Converting Units of Area UnitSymbol Relationship to Square Meter square kilometerkm 2 1,000,000 m 2 square hectometerhm 2 10,000 m 2 square dekameterdam 2 100 m 2 square meterm2m2 base unit square decimeterdm 2 0.01 m 2 square centimetercm 2 0.0001 m 2 square millimetermm 2 0.000001 m 2

7. Slide 7 Example Convert each of the following: a.2 km 2 = _________ m 2 b.7,290,000 cm 2 = _________ m 2 2,000,000 729

8. Slide 8 Unit of AreaEquivalent of Other Units 1 ft 2 144 in 2 or ft 2 1 yd 2 9 ft 2 1 mi 2 3,097,600 yd 2 or 27,878,400 ft 2

9. Slide 9 Land Measure English units acre square mile Metric units a = are (air) ha = hectare km 2 = square kilometer Unit of AreaEquivalent of Other Units 1 a100 m 2 1 ha100 a, or 10,000 m 2, or 1 hm 2 1 km 2 1,000,000 m 2 1 acre4840 yd 2 1 mi 2 640 acres

10. Slide 10 Area of a Rectangle A = 3 x 4 = 12

11. Slide 11 Area of a Parallelogram A = base x height = bh = ag

12. Slide 12 Area of a Triangle

13. Slide 13 Area of a Rhombus

14. Slide 14 Example Find the area: Answer: A = ½ bh = (½)(8)(6) = 24 cm 2

15. Slide 15 Example Find the area: Answer: A= bh = (6)(3) = 18 cm 2

16. Slide 16 Example Find the areas: Answer: A= ½ d 1 d 2 A = (½)(6)(4) = 12 cm 2

17. Slide 17 Area of a Trapezoid

18. Slide 18 Example Find the area: Answer: A = (½)(h)(b 1 + b 2 ) A = (½)(4)(10 + 16) A = 52 cm 2 10 cm

19. Slide 19 Area of a Regular Polygon

20. Slide 20 Area of a Circle

21. Slide 21 Area of a Sector

22. Slide 22 HOMEWORK 11-2 Pages 764 – 766 # 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 34 Brain Teaser