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**Area: Triangles and Trapezoids Lesson 10-2 p.509**

Start the Bellwork Quiz. Have your HW, red pen, and book on your desk. Area: Triangles and Trapezoids Lesson 10-2 p.509

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Triangles When finding the area of triangles, remember that a triangle is half of a parallelogram.

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Triangles Now you can see why the formula for the area of a triangle makes sense: A = bh or A = bh 2

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**Triangles Let’s look at an example: A = bh = 4 (5) = 20 2 2 2**

or 10 ft2 5 feet 4 feet

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Try This Find the areas: 7 miles 3 ft. 5 mi. 12 in. 6 miles

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**Try This Find the areas: 7 miles 3 ft. 5 mi. 12 in. 6 miles 216 in2 or**

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**Try This Find the areas: 7 miles 3 ft. 5 mi. 12 in. 6 miles 216 in2 or**

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**Trapezoids Trapezoids have different formula. It looks like this:**

A = h (b1 + b2) or A = h(b1 + b2) 2 b1 h b2

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**Trapezoids A = h (b1 + b2) or A = h(b1 + b2) 2**

Note that there are 2 bases—base 1 and base 2. The formula takes the average of the two bases multiplied by the height. b1 h b2

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**Trapezoids Let’s try an example: A = h (b1 + b2) A = 3.5 (4 + 6) 2 2**

A = 3.5 (5) = 17.5 ft2 4 ft 3.5 ft 6 feet

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Try This Find the area: 24 mm 12 mm 33 mm

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Try This Find the area: 24 mm 12 mm 342 mm2 33 mm

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Try This Find the area: 4.5 feet 2 feet 4 feet

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Try This Find the area: 4.5 feet 2 feet 13 ft2 4 feet

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Example Some shapes look unusual, but when you remember just 3 formulas, you can calculate the area. Which two shapes do you see in the figure at the left?

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Example There is a square (parallelogram) and a triangle. To find the area, first find the area of the parallelogram and then add it to the area of the triangle.

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**Example The square has an area of A = bh or 3 (3) or 9 ft2.**

The triangle has an area of A = ½ bh or ½ (3) (2) or 3 ft2. The total area if or 12 ft2 3 ft 2 ft

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Try This Find the area: 6 cm 6 cm 4 cm 8 cm

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Try This Here is a hint: 6 cm 6 cm 4 cm 8 cm

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**Try This Here is a hint: For the rectangle: A = bh A = 6 (4) = 24 cm2**

For the trapezoid: A = ½ h (b1 + b2) A = ½ (2) (4 + 6) A = 10 cm2 Total area = = 34 cm2 6 cm 6 cm 4 cm 8 cm

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Try This Is there another way to divide this up? 6 cm 6 cm 4 cm 8 cm

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Try This How about like this: 6 cm 6 cm 4 cm 8 cm

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**Try This How about like this: 6 cm For the rectangle:**

A = bh = 8 (4) = 32 cm2 For the triangle: A = ½ bh = ½ (2) (2) = 2 cm2 The total area is or 34 cm2 6 cm 4 cm 8 cm

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Agenda PA#38 Pp #8-16 even, 17, 19

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**Please start Bellwork #**

HW, red pen book on desk.

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Agenda PA# Workbook pp.83 & 84 Benchmark 3 is Friday.

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