General Information
Subject Area: Mathematics (B.E.S.T.)
Grade: 2
Strand: Geometric Reasoning
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.
