9 -7 Perimeter Warm Up Problem of the

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

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

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 Course 1

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

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

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. * Think of key words in word problems that would indicate perimeter!!! Course 1

Key words: • Border • Around • Fencing • Frame • Rim

9 -7 Perimeter 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. Course 1

What is the side length of a regular hexagonal table cloth if the perimeter is 66. 12 inches? If the border for the table cloth costs $ 3. 49 a yard, how many full yards of border do you need to buy if they sale in whole yards only and how much would it cost?

9 -7 Perimeter Check It Out: Example 1 Find the perimeter of the figure. 3. 3 in. Add all the side lengths. 3. 3 + 4. 2 + 3 4. 2 in. The perimeter is 18 in. 4. 2 in. 3 in. Course 1

9 -7 Perimeter Course 1

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

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

9 -7 Perimeter Additional Example 3 A: 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. 1, 471 = 1, 178 + a Add the known lengths. 1, 471 – 1, 178 = 1, 178 + a – 1, 178 293 = a Subtract 1, 178 from both sides. Side a is 293 mm long. Course 1

9 -7 Perimeter Additional Example 3 B: 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 Find the perimeter. P = 254 The perimeter of the polygon is 254 cm. Course 1

9 -7 Perimeter Additional Example 3 C: 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? 4 w 19 cm l = 4 w l = (4 l = 76 Course 1 Find the length. • 19) Substitute 19 for w. Multiply.

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

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

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

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

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

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

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