Unit 1: Length in Metres

Measuring and Comparing Lengths in Metres

Year Level: 3

Duration: 40 minutes

Class Size: 24 students

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Curriculum Alignment (Australian Curriculum v9)

Strand: Measurement and Geometry
Sub-strand: Using units of measurement

Content Descriptors:

• Identify which metric units are used to measure everyday items; use measurements of familiar items and known units to make estimates (AC9M3M01).
• Measure, order and compare objects using familiar metric units of length (ACMMG061).
• Measure and compare objects using familiar metric units of length, mass and capacity, and instruments with labelled markings (AC9M3M02).

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Learning Objectives

By the end of this lesson, students will be able to:

1. Understand the need for standardised units of measurement for length.
2. Estimate lengths and distances in metres.
3. Measure lengths and distances in metres accurately using a metre ruler.
4. Compare lengths and distances measured in metres and order them accordingly.

(WALT: know the need for standardised units of measurement and length, estimate and measure lengths and distances in metres, compare lengths and distances in metres.)

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Resources

• One 1-metre ruler per group (approx. 6 groups of 4 students each)
• Several tissue boxes
• Measuring blocks or cubes for non-metre length comparison
• Outdoor space suitable for measuring longer objects/items
• Whiteboard and marker or chart paper for group discussion

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Lesson Structure

1. Introduction (7 minutes)

• Engage: Begin with a real-world discussion about measuring things. Ask students:
  • How do they know if something is long or short?
  • Have they ever tried measuring something?
• Show a tissue box and pose questions:
  • What could we measure about this box? (Length, width, height, volume/capacity, mass)
  • Explain that different measurements need different units and tools.
• Emphasise the importance of using standardised units to compare measurements accurately.

2. Exploration and Demonstration (8 minutes)

• Demonstrate:
  • Use measuring blocks to measure the height of two different tissue boxes. Show how using the same unit (blocks vs blocks) is necessary for accurate comparison.
  • Explain why using different units (blocks vs centimetres) directly wouldn’t be fair or accurate.
• Introduce the metre ruler: Show the 1-metre ruler to the class, pointing out the labelled markings. Explain that the metre is a standard metric unit of length used to measure longer objects precisely.

3. Outdoor Hands-on Activity (18 minutes)

• Take the students outdoors in their groups.
• Each group will:
  • Estimate the length and width of various outdoor objects (e.g., bench, garden beds, paths).
  • Then use the metre ruler to measure these objects' lengths and widths accurately.
• Encourage them to write or record their estimates and actual measurements.
• Once measurements are recorded, prompt groups to compare their recorded lengths:
  • Which object is longer?
  • Which is shorter?
  • Are their estimates close to actual measurements? How can they improve their estimating?

4. Group Discussion and Reflection (5 minutes)

• Bring students back together to share their findings.
• Discuss:
  • Why it’s important to use the same measuring units when comparing lengths.
  • How the metre ruler helped them get more accurate measurements than estimating or using informal units.
  • How length and width can be different for the same object and why both can be measured.
• Reinforce the lesson WALT clearly.

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Assessment

• Formative: Teacher observes group participation during outdoor measuring activity, checking if students estimate and measure lengths using the metre ruler correctly.
• Oral questions:
  • Why is it important to use a standard unit of measurement?
  • Can you explain how you compared the lengths of two objects?
• Written or recorded responses: Students record their estimates and actual measures and describe which object was longest/shortest, demonstrating understanding of comparison.

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Differentiation

• For students needing support: Work in smaller groups with adult assistance during measuring. Focus on shorter objects to manage difficulty.
• For advanced students: Challenge them to find items longer than 1 metre and try to measure partial lengths plus how many full metre lengths it contains.

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Teacher Notes

• Use the tissue box example to introduce differences between measurement types: length (metres), capacity (litres), and mass (kilograms).
• Highlight the necessity of consistent metric units when measuring and comparing, i.e., always use metres, not mixed units.
• Focus on both length and width measurements to develop spatial awareness of objects.
• Use this as an opportunity to blend estimating skills with accurate measurement to build confidence in metric understanding.

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This lesson is scaffolded explicitly on the Australian Curriculum (v9) content descriptors AC9M3M01, ACMMG061, AC9M3M02 as specified in the Measurement and Geometry strand, supporting students in understanding and working with familiar metric units of length.