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5-GM-2-3

Page history last edited by Brenda Butz 6 years, 1 month ago

5.GM.2.3 Find the perimeter of polygons and create arguments for reasonable values for the perimeter of shapes that include curves. 


In a Nutshell

In objective 5GM.2.3, students will find the perimeter of polygons by adding all sides.  They will also use estimation skills to find the approximate perimeter measurement for shapes that have curves. Students should be given hands on practice, possibly with estimation and then by actually using a nonstandard measurement tool.  They should be able to explain and defend their thinking.

Student Actions

Teacher Actions

  • Develop the Ability to Make Conjectures, Model, and Generalize by representing pictorially and numerically,  problems related to perimeter.

  • Develop Strategies for Problem Solving by making and testing conjectures about geometric properties and relationships and develop logical arguments to justify conclusions.

  • Develop Strategies for Problem Solving when working to find the perimeter of curved shapes.  For example, they might self-determine that outlining the shape with a piece of string and then measuring the string is an accurate way to find the perimeter.

  • Develop Mathematical Reasoning to apply their logic and create arguments or counter arguments about the perimeter of shapes with curved edges.
  • Implement tasks that promote reasoning and problem solving when determining perimeter of polygons.  For example, the teacher could give the students grid paper, string, rulers, paper strips, etc, and allow the students to explore to find the most accurate measurement.

  • Build procedural fluency from conceptual understanding by providing opportunities for students to articulate the idea that perimeter is found by measuring the length of the sides and adding them up.

  • Use and connect mathematical representations by providing the opportunity for modeling problems using manipulatives and/or a sketching of the problem situation to help students make sense of the measurement they are asked to find as well as an appropriate unit of measurement.

 

Key Understandings

Misconceptions

  • Define a polygon.

  • Understand that the perimeter is the distance around the polygon.

  • Understand that units must be common in order to add.

  • Give an estimate of length to a curved line.

  • Use a nonstandard tool, ie. string, grid paper, etc to measure a curved line.

  • Reason why a given perimeter is valid or invalid.

 

 

  • Try to use the formula for finding the perimeter of rectangular shapes on non-rectangular shapes.

  • Confuse area and perimeter

  • Overgeneralize the definition of perimeter situations.

    • EX. Student interprets all “wall painting” problems as area, even if the problem talks about the length of a striped border that is painted around the room.

  • Count the number of squares in the border instead of the edges of the squares when counting perimeter of dimensions of shapes drawn on a grid .

  • Lack “benchmarks” that allow them to estimate measures. 

 

OKMath Framework Introduction

5th Grade Introduction

 

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