Introduction

• You must use all the rods to make the shape.• The rods may not overlap.Use the rods to create a shape, following the rules. Ask students how they could find the perimeter of theshape. Elicit a variety of responses.Working on ItInstructional Grouping: Pairs, individualsChallenge the students, in pairs, to make a variety of shapes with a perimeter of 18 cm. Explain that studentsmust use only the allotted Cuisenaire rods, and that they must follow the rules explained in “Getting Started”.Have students trace the shapes on grid paper and cut them out.Observe students’ strategies for making shapes that have a perimeter of 18 cm. Some students may need asmall-group guided lesson on perimeter, since a common student misconception in this type of activity is thatthe square units should be counted – students find the area of the shapes rather than the perimeter.Note: Some students may rely on the use of the Cuisenaire rods to form their shapes for the entirety of themathematics lesson. Other students may realize that each rod represents a certain number of units on thegrid paper and may not feel the need to use the rods for tracing. They may go directly to recording theshapes on the centimetre grid paper without the assistance of the manipulatives.Independent Work: Students work independently to make a variety of shapes, using the rules above; they tracethe shapes on centimetre grid paper; and they record the perimeters. Challenge the students to arrange therods to get the shortest perimeter and the longest perimeter. Ask the students, “Can you form more than oneshape with the shortest perimeter and more than one shape with the longest perimeter?” Give the studentssufficient time to work through the problem of finding and recording all the possible shapes with the longestand shortest perimeters.Reflecting and ConnectingInstructional Grouping: Whole classAsk students to explain their methods for finding the perimeter of the different shapes they created. Have studentscompare and discuss different possibilities for making different shapes with the same perimeter.Discuss students’ results in finding the shapes with the longest and the shortest perimeters. Have students usetheir Cuisenaire rods to make the different shapes with the longest and shortest perimeters on the overheadprojector.Draw up a chart that shows all of the shapes with the longest and shortest perimeters. Ask students, “Havewe found all of the possible shapes with the longest and shortest perimeters? How do you know?” Give studentstime to discuss these two questions in pairs or small groups. Have the students share their responseswith the large group.76 A Guide to Effective Instruction in Mathematics, Kindergarten to Grade 6 – Volume One