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

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 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 Perimeter

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

Vocabulary perimeter Insert Lesson Title Here Course Perimeter

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

Course 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 Course 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 Course 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. Course 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? First find the unknown side length. Find the sides opposite side b. The length of side b = Side b is 72 cm long. P = P = 254 Find the perimeter. The perimeter of the polygon is 254 cm. 72 cm Course 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 Course 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 Course 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 Course 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 Course 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 Course 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. Course 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 Insert Lesson Title Here 112 cm 5 6 __ Course 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? Insert Lesson Title Here 60 cm 62 in. Course Perimeter