Measuring PerimeterUnit of Study 8 : Measuring Length and PerimeterGlobal Concept Guide: 3 of 3

Content Development Approximately 4 days should be spent on measuring perimeter.

When all the sides in a shape are not pre-labeled it requires students to make geometrical connections before they calculate perimeter. This can make a fairly straightforward task a bit more complex for students. Examining the properties of shapes while calculating perimeter also prepares students to work with more rigorous tasks later on.

The term perimeter refers to the distance around polygons. Perimeter is not used for example, in the context of circles. The distance around a circle is known as its circumference.

Day 1 The focus of Day 1 is strategies for finding perimeter.

Evaluating the appropriateness of a unit should be embedded within all units in this GCG.

Students develop an understanding of the concept of perimeter

through various real world experiences, such as walking around the perimeter of a room, playground, etc.

Initially grid paper or geo-dot paper should be used to build conceptual understanding.

Misconception Alert: Students may forget to count all the units of a figure, especially if the figure is concave in nature.

Day 2 The focus of Day 2 is using a ruler to calculate the perimeter of

a shape.

Students must be precise when recording measurements, including the number of units counted as well as the unit type.

Estimating perimeter should be embedded within this lesson. Although an estimate of an exact answer can be made before or after finding that answer, we typically ask students to estimate first. Exact answers are then compared to the estimates and judged for reasonableness.

Day 3

The focus of Day 3 is using the attributes of shapes to calculate perimeter or the length of a missing side.

Sample Tasks:

Find the perimeter of the figure.

Missing Side Question

Day 4 The focus of Day 4 is solving perimeter problems by finding

patterns.

The problem solving strategy “Make a Table” should be strongly emphasized during Day 4.

Sample Task: Mr. Ellis is setting up tables and chairs for a party. His tables are triangular. One chair will fit on each side of the table. If Mr. Ellis needs to seat 10 people and he connects tables side to side, how many tables will he need to set up to accommodate all his guests?

Mr. Ellis’ Dilemma

Tables Chairs

1 3

2 4

3 5

Day 4 By the end of Day 4 Students Should be Able to:

Generate reasonable perimeter estimates Choose appropriate units to measure perimeter based on situations

presented Evaluate the efficiency of strategies used to find perimeter Find the perimeter of regular and irregular figures Find the missing side when given the perimeter and lengths of

subsequent sides

Enrich/Reteach/Intervention Reteach:

TE 487B-Students make rectangles with given side lengths and calculate their perimeter.

R102-Students find the perimeter of convex shapes.

Enrich: TE 461B-Draw various shapes based on given perimeters. E102-Students are given a shape and must match it to the correct

expression used to calculate its perimeter.

Literature Connections