Measuring the circumference of a tree (non-standard units)

Curriculum

Measurement and Counting

From the Ontario Ministry of Education Kindergarten Curriculum

  • 3.2: Demonstrate the ability to take turns during activity and discussions (SRWB)
  • 16.1: Select an attribute to measure, determine an appropriate non-standard unit of measure and measure and compare two or more objects (DLMB)
  • 16.2: Investigate strategies and materials used when measuring with non-standard units of measure (DLMB)
  • 13.3: Select and use materials to carry out their own explorations (PSI) 

Context

  • Students have experience working with non-standardized units of measurement
  • The students and teacher sit in an outdoor setting with trees

Materials

  • Yarn 
  • Scissors
  • Pencil
  • Paper
  • Marker
  • Masking tape 

Lesson

Introduction

  • Briefly engage students in a discussion about the measurements of different trees
    • What do you notice about the trees around us?
    • Are they all the same? How are they different?
    • What can you tell me about their height or thickness?
  • Explain that the measurement around the tree is called the circumference. 

Lesson

  • Pick and point to a tree, then have students brainstorm ways to measure the tree’s circumference.
  • Remind students that when comparing the circumference of different trees, the same material must be used to in order to get an accurate comparison.
    • If needed remind students about the rules of measurement (no spaces in between each unit, must start at the beginning, must use the same material when measuring, must not overlap units)
  • As a class, choose one unit of measurement (i.e. yarn) to measure the circumference
  • Discuss why this may be the best unit of measurement. 
  • Demonstrate how to measure the circumference of a tree. 
    • Place the yard around the trunk of the tree. Cut off the amount of yarn that is used to surround the tree: this is the measurement that shows how thick your tree is. 
  • In small groups, have each group measure and record the circumference of their chosen tree.

Closure

  • Take each students’ yarn pieces and order them by length.
    Discuss:

    • Which group had the longest yarn?
    • What does this mean – did they have a tree that was thicker than everyone else’s?

Extensions

  • Measure the yarn lengths with other units of measurements mentioned earlier in your discussion about ways to measure the circumference of a tree. 
    • For example, how many cubes long is group #1’s yarn? Transfer the information about the size of each group’s tree on graph paper. 
  • Tape each group’s yarn to a paper in a circular shape to recreate the circumference of the tree. This helps students visualize the cross-section of the tree’s trunk. 
  • Analyze each group’s circle:
    • Which trees have the larger/smaller circumference? How do you know (i.e. students can infer this from the size of the circle)?
    • Can you name the trees that have bigger circumferences than other?
    • What do they look like in real life – are they thick or thin? 
      • For example, a hill oak tree may have a smaller circumference than a cedar tree.
  • If students are ready, introduce standardized units of measurement and discuss how using yarn to measure circumference can be translated into standardized units of measurement.