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9-7 Perimeter Course 1 Warm Up Warm Up Lesson Presentation Lesson Presentation Problem of the Day Problem of the Day

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Warm Up 1. What figure has four equal sides and four right angles? 2. What figure has eight sides? 3. What figure has five sides? square octagon pentagon Course 1 9-7 Perimeter

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Problem of the Day Find the greatest perimeter possible when 6 identical unit squares are arranged to form a closed figure. Adjacent squares must share an entire side. 14 units Course 1 9-7 Perimeter

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Learn to find the perimeter and missing side lengths of a polygon. Course 1 9-7 Perimeter

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Vocabulary perimeter Insert Lesson Title Here Course 1 9-7 Perimeter

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The perimeter of a figure is the distance around it. To find the perimeter you can add the lengths of the sides. Course 1 9-7 Perimeter

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Additional Example 1: Finding the Perimeter of a Polygon Find the perimeter of the figure. 2.8 + 3.6 + 3.5 + 3 + 4.3 Add all the side lengths. The perimeter is 17.2 in. Course 1 9-7 Perimeter

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Check It Out: Example 1 Find the perimeter of the figure. 3.3 + 3.3 + 4.2 + 4.2 + 3 Add all the side lengths. 3.3 in. 4.2 in. 3 in. The perimeter is 18 in. Course 1 9-7 Perimeter

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Course 1 9-7 Perimeter

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Additional Example 2: Using a Formula to Find Perimeter Find the perimeter P of the rectangle. P = 2l+ 2w Substitute 12 for l and 3 for w. P = (2 12) + (2 3) P = 24 + 6 P = 30 Multiply. Add. The perimeter is 30 cm. 12 cm 3 cm Course 1 9-7 Perimeter

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Check It Out: Example 2 Find the perimeter P of the rectangle. P = 2l + 2w Substitute 15 for l and 2 for w. P = (2 15) + (2 2) P = 30 + 4 P = 34 Multiply. Add. The perimeter is 34 cm. 15 cm 2 cm Course 1 9-7 Perimeter

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What is the length of side a if the perimeter equals 1,471 mm? P = sum of side lengths Use the values you know. 1,471 = 416 + 272 + 201 + 289 + a 1,471 = 1,178 + a 1,471 – 1,178 = 1,178 + a – 1,178 Add the known lengths. Subtract 1,178 from both sides. 293 = a Side a is 293 mm long. Additional Example 3A: Finding Unknown Side Lengths and the Perimeter of a Polygon Find each unknown measure. Course 1 9-7 Perimeter

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Additional Example 3B: Finding Unknown Side Lengths and the Perimeter of a Polygon Find each unknown measure. What is the perimeter of the polygon? First find the unknown side length. Find the sides opposite side b. The length of side b = 50 + 22. Side b is 72 cm long. P = 72 + 55 + 50 + 33 + 22 + 22 P = 254 Find the perimeter. The perimeter of the polygon is 254 cm. 72 cm Course 1 9-7 Perimeter

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l = 4w Find the length. l = (4 19) l = 76 Substitute 19 for w. Multiply. Additional Example 3C: Finding Unknown Side Lengths and the Perimeter of a Polygon The width of a rectangle is 19 cm. What is the perimeter of the rectangle if the length is 4 times the width? 4w4w 19 cm Course 1 9-7 Perimeter

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Additional Example 3C Continued P = 2 l + 2 w Substitute 76 and 19. P = 2(76) + 2 (19) P = 152 + 38 P = 190 Multiply. Add. Use the formula for the perimeter of a rectangle. The perimeter of the rectangle is 190 cm. 4w4w 19 cm Course 1 9-7 Perimeter

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Check It Out: Example 3A Find each unknown measure. What is the length of side a if the perimeter equals 1,302 mm? P = sum of side lengths Use the values you know. 1,302 = 212 + 280 + 250 + 240 + a 1,302 = 982 + a 1,302 – 982 = 982 + a – 982 Add the known lengths. Subtract 982 from both sides. 320 = a Side a is 320 mm long. 212 mm280 mm a 250 mm 240 mm Course 1 9-7 Perimeter

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First find the unknown side length. Find the sides opposite side b. The length of side b = 12 + 4. Side b is 16 m long. P = 14 + 12 + 8 + 4 + 6 + 16 P = 60 Find the perimeter. The perimeter of the polygon is 60 m. Check It Out: Example 3B Find each unknown measure. What is the perimeter of the polygon? 12 m 14 m b m 8 m 6 m 4 m 16 m Course 1 9-7 Perimeter

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l = 5w Find the length. l = (5 13) l = 65 Substitute 13 for w. Multiply. Check It Out: Example 3C The width of a rectangle is 13 cm. What is the perimeter of the rectangle if the length is 5 times the width? 5w5w 13 cm Course 1 9-7 Perimeter

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Check It Out: Example 3C Continued 65 cm 13 cm P = 2 l + 2 w Substitute 65 and 13. P = 2(65) + 2 (13) P = 130 + 26 P = 156 Multiply. Add. Use the formula for the perimeter of a rectangle. The perimeter of the rectangle is 156 cm. Course 1 9-7 Perimeter

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Lesson Quiz: Part I Find each perimeter. 1. 2. 3. What is the perimeter of a polygon with side lengths of 15 cm, 18 cm, 21 cm, 32 cm, and 26 cm? 9 cm 4 ft Insert Lesson Title Here 112 cm 5 6 __ Course 1 9-7 Perimeter

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Lesson Quiz: Part II 4. What is the perimeter of a rectangle with length 22 cm and width 8 cm? 5. The width of a rectangle is 12 in. What is the perimeter of the rectangle if the length is 7 in. longer than the width? Insert Lesson Title Here 60 cm 62 in. Course 1 9-7 Perimeter

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