Mathematics · Year 1 · Measuring My Environment · Term 2

Measuring Length with Informal Units

Using uniform informal units (e.g., blocks, paper clips) to measure and compare lengths.

• ACARA Content Descriptions
• AC9M1M01

About This Topic

In Year 1 Mathematics, students measure length using uniform informal units like blocks, paper clips, or hand spans. They place units end-to-end along objects without gaps or overlaps, counting iterations to determine length. This method lets them compare objects directly, such as deciding if the teacher's desk or a student's book bag is longer by noting more or fewer units.

Aligned with AC9M1M01 in the Australian Curriculum, this topic fits the Measuring My Environment unit. Students justify why identical units ensure fair comparisons, examine how gaps shorten results, and plan ways to measure objects in separate rooms using shared units carried by peers. These practices develop reasoning and problem-solving for future formal measurement.

Active learning works well because students handle physical units on classroom items, instantly seeing and fixing issues like uneven placement through trial and error. Group sharing of measurements encourages explanations of methods, turning abstract ideas into concrete experiences that build confidence and retention.

Key Questions

1. Justify why using the same size unit is crucial when measuring the length of the classroom.
2. Analyze the impact of leaving gaps between measuring tools on the accuracy of measurement.
3. Design a method to compare the length of two objects in different rooms.

Learning Objectives

• Compare the lengths of two or more objects using a consistent informal unit.
• Explain why using the same size unit is essential for accurate length measurement.
• Demonstrate how to measure the length of an object by placing informal units end-to-end without gaps or overlaps.
• Design a strategy to compare the length of objects located in different areas using shared informal units.

Before You Start

Counting and Cardinality

Why: Students need to be able to count the number of informal units used to determine the length of an object.

Comparing Quantities

Why: Students should have experience comparing groups of objects to determine which has more or fewer, which directly relates to comparing lengths.

Key Vocabulary

Length	The distance from one end of an object to the other.
Informal Unit	A non-standard object used for measuring, like a block, paper clip, or hand span.
Measure	To find out the size or amount of something, such as length, using units.
Compare	To look at two or more things to see how they are similar or different.
End-to-end	Placing objects or units in a line, touching one after the other without spaces.

Watch Out for These Misconceptions

Common Misconception

Gaps or overlaps between units do not affect the measurement.

What to Teach Instead

Gaps shorten the measured length while overlaps lengthen it. Students discover this through paired trials on the same object, comparing results side-by-side. Group critiques during sharing sessions reinforce precise placement.

Common Misconception

Any unit size works equally well for all objects.

What to Teach Instead

Larger units yield fewer iterations and less precision. Activities measuring with varied uniform units, like cubes versus clips, show how counts change but comparisons stay consistent if units match. Peer debates clarify justification.

Common Misconception

Longer objects always require fewer units.

What to Teach Instead

Longer objects need more units of the same size. Hands-on comparisons of familiar items in small groups reveal this pattern quickly, with students sketching units to visualize and correct their thinking.

Active Learning Ideas

Scavenger Hunt: Classroom Lengths

Give each small group 20 linking cubes as units. Direct students to find and measure five objects like desks, books, and doors, recording cube counts on charts. Groups report their longest and shortest finds to the class.

30 min·Small Groups

Gap Detective Challenge

Pairs measure a shared rope first with deliberate gaps using straws, then correctly without gaps. They compare counts and draw what went wrong. Discuss as a class why accurate placement matters.

20 min·Pairs

Cross-Room Partners

Pair students across rooms and agree on paper clips as units. Each measures a door height and reports the count back via messenger. Class compares results to see equal lengths.

25 min·Pairs

Unit Size Debate

Whole class views measurements of one object with small blocks versus large erasers. Students vote and justify which gives better detail, then measure in preferred unit.

15 min·Whole Class

Real-World Connections

• Construction workers use non-standard items like bricks or lengths of wood to estimate distances on a building site before precise tools are available.
• Interior designers might use a common object, like a specific type of tile, to compare the width of different furniture pieces when planning a room layout.
• Early childhood educators often use blocks or connecting cubes to help young children understand concepts of length and comparison before introducing rulers.

Assessment Ideas

Quick Check

Provide students with three objects of varying lengths (e.g., a pencil, a book, a crayon) and a set of uniform informal units (e.g., paper clips). Ask students to measure each object and record the number of units. Then, ask them to order the objects from shortest to longest based on their measurements.

Discussion Prompt

Present students with two scenarios: one where an object is measured with consistent units and another where there are significant gaps between units. Ask: 'Which measurement do you think is more accurate and why?' Guide them to explain the importance of placing units without gaps.

Exit Ticket

Give each student a card with a picture of two different classroom objects (e.g., a chair and a table). Ask them to write one sentence explaining how they would compare the lengths of these two objects if they were in different classrooms, using only paper clips as their measuring tool.

Frequently Asked Questions

How to teach measuring length with informal units in Year 1?

Start with familiar objects and concrete units like cubes. Model end-to-end placement without gaps on a whiteboard, then let students practise on desks. Use class charts to record and compare results, building to justifications like why matching units matter. This sequence scaffolds from concrete to abstract reasoning over several lessons.

Why use uniform informal units before formal ones?

Informal units teach iteration and comparison without number lines, focusing on concepts like consistency and accuracy. Students grasp that length is relative to unit size through hands-on work. This foundation prevents later confusion with centimetres, as they already justify methods and spot errors like gaps.

How to address gaps in informal measurements?

Incorporate deliberate error activities where pairs measure with gaps, then fix them. Visual aids like string outlines help students align units tightly. Class discussions of discrepant results, such as shorter counts, cement the need for contact, turning mistakes into learning moments.

How does active learning help with informal length measurement?

Active tasks like group hunts and partner comparisons make students manipulate units physically, revealing errors immediately through touch and sight. Collaboration prompts explanations, such as defending unit choices, deepening understanding. These experiences outperform worksheets, as children retain justification skills longer through real-world application and peer feedback.

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