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© 2007 M. Tallman. The area of this rectangle is 40 cm². If you divide this rectangle in half, what two shapes do you see? A = 40 cm²

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Presentation on theme: "© 2007 M. Tallman. The area of this rectangle is 40 cm². If you divide this rectangle in half, what two shapes do you see? A = 40 cm²"— Presentation transcript:

1 © 2007 M. Tallman

2 The area of this rectangle is 40 cm². If you divide this rectangle in half, what two shapes do you see? A = 40 cm²

3 The area of this rectangle is 40 cm². If you divide this rectangle in half, what two shapes do you see? Triangles So if the rectangles area is 40 cm², what is ½ of the rectangles area? 20 cm² A = 20 cm² A = 40 cm²

4 © 2007 M. Tallman The area of this parallelogram is 64 cm². If you divide this parallelogram in half, what two shapes do you see? A = 64 cm²

5 The area of this parallelogram is 64 cm². If you divide this parallelogram in half, what two shapes do you see? Triangles So if the parallelograms area is 64 cm², what is ½ of the parallelograms area? 32 cm² A = 32 cm² A = 64 cm²

6 © 2007 M. Tallman Since triangles are ½ of a rectangle or parallelogram, the formula for finding the area of triangles is A = ½bh. A=8 cm×5 cm A=40cm² A=8 cm×5 cm A=20cm² ½ × A=4 cm×5 cm

7 © 2007 M. Tallman Since triangles are ½ of a rectangle or parallelogram, the formula for finding the area of triangles is A = ½bh. A=8 cm×8 cm A=64cm² A=8 cm×8 cm A=32cm² ½ × A=4 cm×8 cm

8 © 2007 M. Tallman If you know the base (b) and the height (h) of a triangle, you can use a formula to find its area. If you multiply the ½ × b × h, you get the area (A). A = ½ × b × h or A = ½bh A= 6 cm×3 cm A=9cm² ½ × A=3 cm× A= 4 cm×5 cm A=10cm² ½ × A=2 cm×5 cm A= 6 cm×7 cm A=21cm² ½ × A=3 cm×7 cm

9 © 2007 M. Tallman The way the factors are grouped does not change the product. The associative property can make finding the area of a triangle easier! = 24 3 2 x x 4 () (4 × 3) × 2 = 4 × (3 × 2)

10 © 2007 M. Tallman (½ × h) × b ½b ()A=××h (½ × b) × h= ½ × (b × h) = Group the factors in which ever way that makes the problem easier to solve. The way the factors are grouped does not change the product. The associative property can make finding the area of a triangle easier!

11 © 2007 M. Tallman Use the formula A = ½bh to find the area of the triangle. 8 ft A =8 ft) ×9 ft A=36ft² 9 ft (½ × A=4 ft×9 ft

12 © 2007 M. Tallman Use the formula A = ½bh to find the area of the triangle. 20 yd A =20 yd) ×14 yd A=140yd² 14 yd (½ × A=10 yd×14 yd

13 © 2007 M. Tallman Use the formula A = ½bh to find the area of the triangle. 16 m A =16 m) ×9 m A=72m² 9 m (½ × A=8 m×9 m

14 © 2007 M. Tallman Use the formula A = ½bh to find the area of the triangle. 7 in A =7 in ×10 in A=35in² 10 in ½ × A= 7 in× 5 in

15 © 2007 M. Tallman Use the formula A = ½bh to find the area of the triangle. 11 mm A =(11 mm ×6 mm) A=33mm² 6 mm ½ × A=11 mm×6 mm

16 © 2007 M. Tallman A=36units²

17 A=27.5units²

18 A=24units²

19 A=20units²

20 A=9units²

21 A=16units²

22 A=21units²

23 6 mm 8 mm b A = 24 mm² 24 mm² ×= 248 mm² 48 mm²÷8 mm=6 mm

24 8.5 ft h 14 ft A = 59.5 ft² 59.5 ft² ×= 2119 ft² 119 ft²÷14 ft=8.5 ft

25 12 in b 9 in A = 54 in² 54 in² ×= 2108 in² 108 in²÷9 in=12 in

26 11.5 ft 7 ft h A = 40.25 ft² 40.25 ft² ×= 280.5 ft² 80.5 ft²÷7 ft=11.5 ft

27 8 yd b A = 48 yd² 48 yd² ×= 296 yd² 96 yd²÷12 yd=8 yd 12 yd


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