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

## Curriculum

#### Measurement and Counting

• 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

• Yarn
• Scissors
• Pencil
• Paper
• Marker

## 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. 