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Learn to find the perimeter and missing side lengths of a polygon .

9-7. Perimeter. Course 1. Learn to find the perimeter and missing side lengths of a polygon. 9-7. Perimeter. Course 1. Insert Lesson Title Here. Vocabulary. perimeter. 9-7. Perimeter. Course 1.

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Learn to find the perimeter and missing side lengths of a polygon .

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

  2. 9-7 Perimeter Course 1 Insert Lesson Title Here Vocabulary perimeter

  3. 9-7 Perimeter Course 1 The perimeter of a figure is the distance around it. To find the perimeter you can add the lengths of the sides.

  4. 9-7 Perimeter Course 1 Additional Example 1: Finding the Perimeter of a Polygon Find the perimeter of the figure. Add all the side lengths. 2.8 + 3.6 + 3.5 + 3 + 4.3 The perimeter is 17.2 in.

  5. 9-7 Perimeter Course 1 Check It Out: Example 1 Find the perimeter of the figure. 3.3 in. 3.3 in. Add all the side lengths. 3.3 + 3.3 + 4.2 + 4.2 + 3 The perimeter is 18 in. 4.2 in. 4.2 in. 3 in.

  6. 9-7 Perimeter Course 1

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

  8. 9-7 Perimeter Course 1 Check It Out: Example 2 Find the perimeter P of the rectangle. 15 cm 2 cm P = 2l + 2w Substitute 15 for l and 2 for w. P = (2 •15) + (2 •2) P = 30 + 4 Multiply. P = 34 Add. The perimeter is 34 cm.

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

  10. 9-7 Perimeter Course 1 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. 72 cm 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 Find the perimeter. P = 254 The perimeter of the polygon is 254 cm.

  11. 9-7 Perimeter Course 1 Additional Example 3C Continued 4w 19 cm Use the formula for the perimeter of a rectangle. P = 2l + 2w Substitute 76and 19. P = 2(76) + 2 (19) P = 152 + 38 Multiply. P = 190 Add. The perimeter of the rectangle is 190 cm.

  12. 9-7 Perimeter Course 1 Check It Out: Example 3A Find each unknown measure. What is the length of side a if the perimeter equals 1,302 mm? 212 mm 280 mm 250 mm a P = sum of side lengths 240 mm 1,302 = 212 + 280 + 250 + 240 + a Use the values you know. Add the known lengths. 1,302 = 982 + a 1,302 – 982 = 320 Subtract 982 from both sides. a = 320 Side a is 320 mm long.

  13. 9-7 Perimeter Course 1 Check It Out: Example 3B Find each unknown measure. What is the perimeter of the polygon? 12 m 8 m First find the unknown side length. 14 m 4 m Find the sides opposite side b. 6 m The length of side b = 12 + 4. 16 m b m Side b is 16 m long. P = 14 + 12 + 8 + 4 + 6 + 16 Find the perimeter. P = 60 The perimeter of the polygon is 60 m.

  14. 9-7 Perimeter Course 1 Check It Out: Example 3C Continued 65 cm 13 cm Use the formula for the perimeter of a rectangle. P = 2l + 2w Substitute 65and 13. P = 2(65) + 2 (13) P = 130 + 26 Multiply. P = 156 Add. The perimeter of the rectangle is 156 cm.

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