AC9M4M02
Official content description
recognise ways of measuring and approximating the perimeter and area of shapes and enclosed spaces, using appropriate formal and informal units
What AC9M4M02 actually looks like when you teach it
Perimeter and area are taught together and confused constantly, so make the distinction physical before it becomes numerical. Perimeter is the walk around the edge; area is the paint needed to cover it. Give them square tiles and let them cover shapes rather than calculating, and string to lay around the outside. The most valuable task in this unit is the one where two shapes share a perimeter but not an area — it breaks the assumption that the two must move together, which is the assumption behind most of the errors.
What the class will get wrong — and what to do about it
The error
Assuming that shapes with the same perimeter have the same area, or using the perimeter formula when asked for area and vice versa.
How to confront it
Give every pair 12 square tiles and ask them to make as many different rectangles as they can. Same area, different perimeters. Then do the reverse with a fixed loop of string. Two tasks, and the link is permanently broken.
Ready to put on the board
We are learning to measure and compare perimeter and area.
- I can explain the difference between perimeter and area.
- I can find the perimeter of a shape by measuring its sides.
- I can find the area of a shape by covering it with units.
Twelve tiles
- Each pair makes every rectangle they can using all 12 tiles. There are three: 1×12, 2×6, 3×4.
- Record each on grid paper and label the area. It's 12 every time — they used all the tiles.
- Now measure the perimeter of each. They differ: 26, 16, 14.
- Ask the question directly: same area, same perimeter? Write the conclusion in their own words.
- Extension: which rectangle would need the least fencing? This is the shape of every real perimeter problem they'll meet.
Free to use in your classroom. Written for AC9M4M02, not adapted from another year level.
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The Year 4 Maths planning scaffold
A one-page planning sheet with the official achievement standard, every content description grouped by strand, and space for your assessment and week-by-week sequence. Print it and plan on paper, or use it as the skeleton for a unit.
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What Year 4 Maths students should achieve
Coverage is judged against the achievement standard — not by ticking every content description. These are the official Year 4 Maths standard sentences this code builds towards:
- They recognise equivalent fractions and make connections between fraction and decimal notations.
- Students order events or the outcomes of chance experiments in terms of likelihood and identify whether events are independent or dependent.
- They use mathematical modelling to solve financial and other practical problems, formulating the problem using number sentences, solving the problem choosing efficient strategies and interpreting results in terms of the situation.
- They find unknown values in numerical equations involving addition and subtraction.
- Students use the properties of odd and even numbers.
- They choose rounding and estimation strategies to determine whether results of calculations are reasonable.
The Measurement progression either side of AC9M4M02
A class can only meet this descriptor if they were taught the one before it. If yours hasn't, that's where the lesson starts — not here.
Taught before · Year 3
- AC9M3M01identify which metric units are used to measure everyday items; use measurements of familiar items and known units to make estimates
- AC9M3M02measure and compare objects using familiar metric units of length, mass and capacity, and instruments with labelled markings
- AC9M3M03recognise and use the relationship between formal units of time including days, hours, minutes and seconds to estimate and compare the duration of events
Builds towards · Year 5
- AC9M5M01choose appropriate metric units when measuring the length, mass and capacity of objects; use smaller units or a combination of units to obtain a more accurate measure
- AC9M5M02solve practical problems involving the perimeter and area of regular and irregular shapes using appropriate metric units
- AC9M5M03compare 12- and 24-hour time systems and solve practical problems involving the conversion between them
Other Year 4 Measurement codes
- AC9M4M01interpret unmarked and partial units when measuring and comparing attributes of length, mass, capacity, duration and temperature, using scaled and digital instruments and appropriate units
- AC9M4M03solve problems involving the duration of time including situations involving “am” and “pm” and conversions between units of time
- AC9M4M04estimate and compare angles using angle names including acute, obtuse, straight angle, reflex and revolution, and recognise their relationship to a right angle
Content description and achievement standard © Australian Curriculum, Assessment and Reporting Authority (ACARA), Australian Curriculum Version 9, used under CC BY 4.0. TeachKoala is not affiliated with or endorsed by ACARA.