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NJ ASK POD In math class, Eddie drew an isosceles, acute triangle. One of the angles has a measure of 42 degrees. What are the other two angle measures of Eddie’s triangle? DO NOW A square and a regular hexagon have the same perimeter. A side of the square is 4.5 inches long. How long is a side of the hexagon?
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HW and POW Review – Pg. 538 #1,5,8 Pg. 542 #1,4,7 Pg.548 #1,3,5 Pg.552 #4
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Objective TLWBAT create a composite figure of the initials of one’s name by combining different polygons and calculate the area of the figure by applying the appropriate formulas to earn a rubric score of at least 8 out of 10 points. NJCCCS 4.2.7.E.1 Common Core 7.G.B.4, 7.G.B.6
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Estimating the Area of an Irregular Figure Estimate the area of the figure. Each square represents one square yard. Count the number of filled or almost-filled squares: 45 squares. Count the number of squares that are about half-full: 10 squares. Add the number of filled squares plus ½ the number of half-filled squares: 45 + ( 10) = 45 + 5 =50 1212 The area of the figure is about 50 yd 2.
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Check It Out: Example 1 Estimate the area of the figure. Each square represents one square yard. Count the number of filled or almost-filled squares: 11 red squares. Count the number of squares that are about half-full: 8 green squares. Add the number of filled squares plus ½ the number of half-filled squares: 11 + ( 8) = 11 + 4 =15. 1212 The area of the figure is about 15 yd. 2
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Example 2: Finding the Area of an Irregular Figure Find the area of the irregular figure. Use 3.14 for . Use the formula for the area of a parallelogram. Substitute 16 for b. Substitute 9 for h. A = bh A = 16 9 A = 144Step 1: Separate the figure into smaller, familiar figures. 16 m 9 m 16 m Step 2: Find the area of each smaller figure. Area of the parallelogram:
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Example 2 Continued Find the area of the irregular figure. Use 3.14 for . Substitute 3.14 for and 8 for r. 16 m 9 m 16 m Area of the semicircle: A = (r) 1 2 __ The area of a semicircle is the area of a circle. 1212 A ≈ (3.14 8 2 ) 1 2 __ A ≈ (200.96) 1 2 __ Multiply. A ≈ 100.48
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Example 2 Continued Find the area of the irregular figure. Use 3.14 for . A ≈ 144 + 100.48 = 244.48The area of the figure is about 244.48 m 2. Step 3: Add the area to find the total area. 16 m 9 m 16 m
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Check It Out: Example 3 Find the area of the irregular figure. Use 3.14 for . Use the formula for the area of a rectangle. Substitute 8 for l. Substitute 9 for w. A = lw A = 8 9 A = 72Step 1: Separate the figure into smaller, familiar figures. 3 yd 9 yd Step 2: Find the area of each smaller figure. Area of the rectangle: 8 yd 9 yd
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Check It Out: Example 3 Continued Find the area of the irregular figure. Use 3.14 for . Substitute 2 for b and 9 for h. Area of the triangle: A = bh 1 2 __ The area of a triangle is the b h. 1212 A = (2 9) 1 2 __ A = (18) 1 2 __ Multiply. A = 9 2 yd 9 yd 8 yd 9 yd
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Check It Out: Example 3 Continued Find the area of the irregular figure. Use 3.14 for . A = 72 + 9 = 81The area of the figure is about 81 yd 2.Step 3: Add the area to find the total area.
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Problem Solving Application The Wrights want to tile their entry with one- square-foot tiles. How much tile will they need? 5 ft 8 ft 4 ft 7 ft t
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Find the area of the floor by separating the figure into familiar figures: a rectangle and a trapezoid. Then add the areas of the rectangle and trapezoid to find the total area. 5 ft 8 ft 4 ft 7 ft t
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Find the area of each smaller figure. A = lw A = 8 5 A = 40 Area of the rectangle: Area of the trapezoid: A = 24 A = h(b 1 + b 2 ) 1 2 __ A = 4(5 + 7) 1 2 __ A = 4 (12) 1 2 __ Add the areas to find the total area. A = 40 + 24 = 64 The Wrights’ need 64 ft 2 of tile. 5 ft 8 ft 4 ft 7 ft t
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Lesson Quiz Find the perimeter and area of each figure. 1. 2. 31.42 cm, 62.13 cm 2 39.1 ft, 84 ft 2
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3. Identify the perimeter and area of the figure. A. 50 cm; 42 cm 2 B. 50 cm; 54 cm 2 C. 34 cm; 54 cm 2 D. 34 cm; 42 cm 2 Lesson Quiz
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4. Identify the perimeter and area of the figure. A. 14.85 in.; 31.63 in 2 B. 22.7 in.; 31.63 in 2 C. 14.85 in.; 15.81 in 2 D. 22.7 in.; 15.81 in 2 Lesson Quiz
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Closure Find the area by breaking the composite figure into familiar shapes.
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