EXT 3-6 Sampler

41 Grade3 PartB 77 ©Math TeachersPress, Inc.,Reproduction by anymeans is strictly prohibited. Part B 1. Perimeter = 12 units 2 lengths= _______ units 1 length = _______ units 2. Perimeter = 14 units 2widths = _______ units 1width = _______ units Finding theMissingSide of aRectangle Perimeter is the distance around the outside of a figure. Jay wants to buy fencing to enclose a garden. The garden is 2 feet wide and 5 feet long. Howmuch fencing should he buy? Sue has 20 inches of wood tomake a picture frame. The framemust be 6 inches long. How long is one of the shorter sides? The perimeter and the length of 1 side is given. Find the length of themissing side. Perimeter ( P ) = 5 + 2 + 5 + 2 = _______ feet 5 feet 2 feet length = 4 units length = ? width = 2 units width = ? 3. Perimeter = 28 inches 2widths = _______ inches 1width = _______ inches 4. Perimeter = 30 inches 2 lengths= _______ inches 1 length = _______ inches 10 inches width = ? length = ? width = 5 inches 6 inches 6 inches ? ? Think: 20 – (2 6) = ____ inches To find the width of one of the sides, _________________by 2. Shortest side = ____ inches 14 8 divide 8 8 6 20 4 4 3 10 4 Lesson 28, 3ETeacher 77 Objective53: To find themissing sideof a rectangle whengiven theperimeter and lengthof 1 side. Touse theworkingbackwards strategy. Materials: Cut out rectangles 4 cmby6 cm, Centimeter GraphPaper (Master 9), scissors WorkingBackwardsToFindMissingSides In this lesson, studentswill learn to think about the “workingbackwards strategy” to find themissing sideof a rectangle. Reviewpages 58 and59onhow to find the perimeter of a rectangle that is 5 cm long and2 cmwide. Whatdoesperimetermean?Canyoudrawapicture to solve theproblem? Eachgroupwill need a4 cmby6 cm rectangle and a 20-centimeter stripof graphpaper (cut from the long side ofMaster 9). Nowwewill learnhow toworkbackwards to solveaproblem. Supposeweknow theperimeterand lengthof 1 sideof a rectangle.How canwe find the lengthof amissing side? Writeon theboard: Youhave20 feet of chickenwire tomake a fence around a rectangular area. The shorter sides of the fencewill be4 feet long. Find the lengthof oneof the longer sides. Direct the students’ attention to the20 centimeter strip of graphpaper. This is a small scalemodel of the chicken wire fence that is 20 feet long. Eachof theseunits stands for 1 foot of length.Canyoudraw apictureof the problem?Allow time for students todiscuss solutions in their group. Whatdoweknow in thisproblem? (theperimeter and lengthof the2 short sides) Canyouuse this information to find the lengthof themissing side? One solution: I laid outmy20-unit strip. I shaded4units and4units to equal 5 cm 2 cm P= 5+ 2+ 5+ 2= 14 cm 4 ft. 4 ft. Perimeter = 20 ft. the shorter sides. Then I countedhowmanyunitswere left. Therewere12 centimeters left for the2 equal longer sides. So, I divided12by2 toget 6 centimeters. We call thisworkingbackwardsbecausewe started with theperimeterand lengthof some sides andworked backwards to findamissing side. Read the information together at the topof thepage. Have studentsdiscuss andwrite the correct answer in each blank. Workproblems 1 and3 together. Students are to solve problems 2 and4 independently. Skill Builders 53-1 20 units 4 4 3.MD.8 FindingMissingSideofaRectangle Students learn theworking backwards strategy to find the lengthof amissing side.