Content description: recognise ways of measuring and approximating the perimeter and area of shapes and enclosed spaces, using appropriate formal and informal units
E1: recognising that perimeter is the sum of the lengths that form the boundary of a shape or enclosed space; choosing suitable units from a range of objects to measure around the boundary of a shape such as a garden bed; comparing the results to say which unit was an appropriate choice for the context; using a piece of string or rope to measure the perimeter of irregular shapes and enclosed spaces, including those that have curved sections
Teach and measure: Walk a finger once around a rectangle, adding all boundary sides. Choose a fixed informal length unit for a garden-bed model, then compare with centimetres or metres. For a curved or irregular edge, fit string or rope around it, mark the meeting point, straighten and measure. Repeat and explain an approximate result. Evidence: actual full-boundary measuring, a suitable unit and a method that includes curved sections.
E2: creating a range of rectangles representing “paddocks” on grid paper and establishing different methods of working out the length of the boundary fences; explaining that the more efficient methods involve adding the side lengths rather than counting squares
Create paddocks: Draw rectangles on grid paper using different side-length pairs. For area 24 square units, compare the 1 by 24, 2 by 12, 3 by 8 and 4 by 6 examples above. Label the four sides and calculate each boundary sum. Teacher asks: “Why is adding 4 + 6 + 4 + 6 quicker than counting twenty short edges?” Evidence: actual drawings, correctly labelled boundaries and explained efficient addition.
E3: recognising that area is the space enclosed by the boundary of a shape or the surface of an object; measuring and comparing the area of shapes, using an array of paper tiles or mosaic squares, including part units to fill gaps at the edge of the shapes; comparing the total areas by combining the fractional parts to make whole units
Cover and combine: Use equal paper tiles to cover a rectangle and a shape with a sloping edge. A triangle may cover six whole squares and four halves, making eight square units. Pair halves or combine quarters from the same unit. Compare: seven whole squares plus two halves equals six whole plus four halves: both are eight square units. Look for: complete surface coverage and recorded full/part totals.
E4: demonstrating how to use one unit repeatedly to measure the area of a shape; for example, using one paper square to measure and compare the area of a rectangle and a triangle; recording and explaining how they used part units to give a more accurate measure, and why they needed to ensure there were no gaps or overlaps
Use one unit repeatedly: Give each learner only one paper square. They move, trace and number its positions on a rectangle, then a triangle. Record the full-square count and combined part count; show why no surface is skipped or counted twice. Evidence: actual repeated placement, marked positions, a stated unit and a justified total. Choosing a multiple-choice method alone does not demonstrate this practical skill.
E5: investigating the ways First Nations Ranger Groups and other groups measure areas of land to make decisions about fire burns to care for Country/Place
Public context: The ALFA (NT) 2020 annual report, pages 56–57, describes Mimal Rangers mapping patches of unburnt land to assess wildfire risk, with GIS and mapped information alongside local Indigenous knowledge. This is a specific published example of mapped areas contributing to fire-related decisions about caring for Country/Place.
Classroom investigation: Read the account with an adult, discuss why the amount and location of land matters, then make an invented equal-square map like the one above. Compare covered areas, including parts of squares. State which comparison the model supports and what it cannot establish. Do not invent cultural meanings, reproduce restricted knowledge or use classroom maps to plan a real burn.