MA.2.GR.2.1

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Explore perimeter as an attribute of a figure by placing unit segments along the boundary without gaps or overlaps. Find perimeters of rectangles by counting unit segments.

Clarifications

Clarification 1: Instruction emphasizes the conceptual understanding that perimeter is an attribute that can be measured for a two-dimensional figure.

Clarification 2: Instruction includes real-world objects, such as picture frames or desktops.

General Information
Subject Area: Mathematics (B.E.S.T.)
Grade: 2
Strand: Geometric Reasoning
Standard: Describe perimeter and find the perimeter of polygons.
Date Adopted or Revised: 08/20
Status: State Board Approved

Benchmark Instructional Guide

Connecting Benchmarks/Horizontal Alignment

 

Terms from the K-12 Glossary

  • Rectangle

 

Vertical Alignment

Previous Benchmarks

  • Perimeter is a new concept in grade 2.

 

Next Benchmarks

 

Purpose and Instructional Strategies

The purpose of this benchmark is to introduce the concept of perimeter as a measurement attribute along the exterior of a two-dimensional figure that can be determined by counting unit segments (MTR.5.1). 
  • Instruction includes the understanding that the measurement is only valid when units are placed and counted without space or overlay. 
  • Instruction includes informal language of length and width.

 

Common Misconceptions or Errors

  • Students may miscount or double count the number of unit segments.

 

Strategies to Support Tiered Instruction

  • Instruction includes teacher modeling how to make tic marks on each unit as you count around the edge of a figure. 
  • Instruction includes the opportunity to use tiles to mark the edge of a figure before touching and counting the units to find the perimeter. Teacher makes a connection to the drawn figure with tic marks. 
  • Instruction includes showing how to line up a ruler. Students measure an unsharpened pencil with the ruler and then verify by lining up 1-inch tiles. 
  • Teacher measures an object using tiles but leaving gaps. Then, the teacher measures the same object again but this time ensuring there are no gaps and uses the tiles to illustrate how leaving gaps can change the measurement.

 

Instructional Tasks

Instructional Task 1 (MTR.2.1, MTR.4.1) 

Provide students with centimeter cubes or snap cubes. 
  • Part A. Using centimeter cubes or snap cubes, construct several rectangles (12” by 6,” 5” by 3,” 14” by 8”). 
  • Part B. Determine the perimeter of each rectangle constructed. What do you notice about the numbers of cubes and the perimeter?

 

Instructional Items

Instructional Item 1 

A student lays down unit cubes to find the perimeter of a rectangle. If the student determines the length is 30-unit cubes long, explain what they may have done incorrectly. 

 

unit cubes in a rectangle

*The strategies, tasks and items included in the B1G-M are examples and should not be considered comprehensive.

Related Courses

This benchmark is part of these courses.
5012040: Grade Two Mathematics (Specifically in versions: 2014 - 2015, 2015 - 2022, 2022 - 2024, 2024 and beyond (current))
7712030: Access Mathematics Grade 2 (Specifically in versions: 2014 - 2015, 2015 - 2018, 2018 - 2022, 2022 and beyond (current))
5012005: Foundational Skills in Mathematics K-2 (Specifically in versions: 2019 - 2022, 2022 - 2024, 2024 and beyond (current))

Related Access Points

Alternate version of this benchmark for students with significant cognitive disabilities.
MA.2.GR.2.AP.1: Explore perimeter as an attribute of a figure that can be measured by placing unit segments along the boundary without gaps or overlaps. Find perimeters of rectangles by counting unit segments.

Related Resources

Vetted resources educators can use to teach the concepts and skills in this benchmark.

Lesson Plans

A Table For 36 Please:

This lesson reinforces perimeter as students arrange tables to decorate.




Type: Lesson Plan

Finding Perimeter by Counting Unit Segments:

In this lesson, students will explore a real world problem based on the Marilyn Burns book Spaghetti and Meatballs for All!. The problem and further practice finding the distance around rectangles will lead them to conceptually understand finding the perimeter of rectangles.

Type: Lesson Plan

Perspectives Video: Expert

B.E.S.T. Journey:

What roles do exploration, procedural reliability, automaticity, and procedural fluency play in a student's journey through the B.E.S.T. benchmarks? Dr. Lawrence Gray explains the path through the B.E.S.T. mathematics benchmarks in this Expert Perspectives video.

Type: Perspectives Video: Expert

Student Resources

Vetted resources students can use to learn the concepts and skills in this benchmark.

Parent Resources

Vetted resources caregivers can use to help students learn the concepts and skills in this benchmark.