Primary 3 maths · Measurement & time · About 10 minutes
Find areas of rectangles and squares
Identify the surface to cover and the lengths that determine its rows. Keep missing or overlapping pieces visible.
Start the interactive lesson →Open practice activity
What you will learn
- Find areas of rectangles and squares
Models used: number sentences, stories, diagrams.
Before you start
Covering a surface, or going around it?
The first row has 5 squares. Each square is one unit of area.
Each little square is one square unit. There are 5 squares across and 3 rows.
The first row has 5 squares. Each square is one unit of area.
Equal rows of squares explain area. Joining or removing surfaces changes how many squares are covered.
Each little square is one square unit. There are 5 squares across and 3 rows.
There are three identical rows. Count five, three times.
5 × 3 = 15 square units
Perimeter asks a different question: how far around the outside? Trace all four sides.
5 + 3 + 5 + 3 = 16 units
Trace the boundary of the rectangle.
What did the picture help us see?
Perimeter asks a different question: how far around the outside? Trace all four sides.
Worked example: A new example, together
Find the area of the 9 cm by 7 cm rectangle.
Identify the surface to cover and the lengths that determine its rows. Keep missing or overlapping pieces visible.
Area counts the surface covered by square units, with missing parts removed.
Dimensions describe the boundary and the covered surface. The full rectangle covers 9 × 7 = 63 square centimetres.
Dimensions describe the boundary and the covered surface. Find the area of the 9 cm by 7 cm rectangle.
63 cm²
The full rectangle covers 9 × 7 = 63 square centimetres.
Dimensions describe the boundary and the covered surface. Each row has the same number of squares.
Dimensions describe the boundary and the covered surface. Area = 63 cm².
Dimensions describe the boundary and the covered surface. Check the result against the question we started with.
63 ÷ 9 = 7.
We found 63 cm². Area counts the surface covered by square units, with missing parts removed.
Dimensions describe the boundary and the covered surface.
Common mistakes to discuss
- Adding the two sides. Area multiplies the sides; perimeter adds them. A 5 cm by 3 cm rectangle has area 15 cm² and perimeter 16 cm.
Check your understanding
- Find areas of rectangles and squares
- explain area calculations using covered square units
- check the answer against the original quantities and units
Explain your reasoning to an adult, then try a fresh question in the interactive lesson. A result from one attempt is not proof of lasting mastery.
Try this lesson →Related Primary 3 lessons
- Add and subtract money in decimal notationAdd and subtract money in decimal notation · About 10 minutes
- Measure length in kilometres and liquid volume in millilitresMeasure length in kilometres and liquid volume in millilitres · About 10 minutes
- Use compound measurement unitsUse compound measurement units · About 10 minutes
- Convert km and m; m and cm; kg and g; litres and mlConvert km and m; m and cm; kg and g; litres and ml · About 10 minutes
- Use seconds as a unit of timeUse seconds as a unit of time · About 10 minutes
- Find start times, finish times and durationsFind start times, finish times and durations · About 10 minutes