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

9-7 Perimeter 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

9-7 Perimeter 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

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

9-7 Perimeter Vocabulary perimeter

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

9-7 Perimeter Additional Example 1: Finding the Perimeter of a Polygon Find the perimeter of the figure Add all the side lengths. The perimeter is 17.2 in = 18 Estimate the perimeter.

9-7 Perimeter Check It Out: Example 1 Find the perimeter of the figure Add all the side lengths. 3.3 in. 4.2 in. 3 in. The perimeter is 18 in = 17 Estimate the perimeter

9-7 Perimeter

9-7 Perimeter 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 = P = 30 Multiply. Add. The perimeter is 30 cm. 12 cm 3 cm

9-7 Perimeter 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 = P = 34 Multiply. Add. The perimeter is 34 cm. 15 cm 2 cm

9-7 Perimeter 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 = 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.

9-7 Perimeter Additional Example 3B: Finding Unknown Side Lengths and the Perimeter of a Polygon Find each unknown measure. What is the perimeter of the polygon? Step 1: Find b. Find the sum of the lengths opposite side b. b = b = 72 P = P = 254 Step 2: Find the perimeter. The perimeter of the polygon is 254 cm.

9-7 Perimeter 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

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

9-7 Perimeter 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 = a 1,302 = a 1,302 – 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

9-7 Perimeter First find the unknown side length. Find the sides opposite side b. The length of side b = Side b is 16 m long. P = 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

9-7 Perimeter 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

9-7 Perimeter 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 = P = 156 Multiply. Add. Use the formula for the perimeter of a rectangle. The perimeter of the rectangle is 156 cm.

9-7 Perimeter Standard Lesson Quiz Lesson Quizzes Lesson Quiz for Student Response Systems

9-7 Perimeter Lesson Quiz: Part I Find each perimeter 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 112 cm 5 6 __

9-7 Perimeter 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? 60 cm 62 in.

9-7 Perimeter 1. Identify the perimeter. A. B. C. D. Lesson Quiz for Student Response Systems

9-7 Perimeter 2. Identify the perimeter. A. 15 cm B. 16 cm C. 17 cm D. 18 cm Lesson Quiz for Student Response Systems

9-7 Perimeter 3. What is the perimeter of a polygon with side lengths 14 cm, 16 cm, 19 cm, 31 cm, and 25 cm? A. 115 cm B. 105 cm C. 95 cm D. 85 cm Lesson Quiz for Student Response Systems

9-7 Perimeter 4. What is the perimeter of a rectangle with length 28 cm and width 9 cm? A. 71 cm B. 72 cm C. 73 cm D. 74 cm Lesson Quiz for Student Response Systems

9-7 Perimeter 5. The width of a rectangle is 14 in. What is the perimeter of the rectangle if the length is 9 in. longer than the width? A. 74 in. B. 75 in. C. 76 in. D. 77 in. Lesson Quiz for Student Response Systems