Angles
An angle measures the amount of turn between two lines that meet at a point. Angles are measured in degrees (°); a right angle is 90° and a full turn is 360°.
Maths · Ages 10–11 · 55 minutes
Area and perimeter
Pupils find the perimeter and area of rectangles and right-angled triangles, use the correct units, and explain the difference between the two measures.
Success criteria
- I can find perimeter by adding all the sides
- I can find the area of a rectangle by multiplying length by width
- I can find the area of a triangle as half a rectangle
Key vocabulary
- perimeter
- area
- length
- width
- base
- height
- square centimetre
- cm²
- formula
You will need
- squared paper
- rulers
- scissors
- string
- mini whiteboards
Curriculum links
- Year 6· England
- Grade 5· United States
- Primary 6· Nigeria
- Class 6· India
- Common Core 3.MD.D.8: Solve problems about the perimeters of polygons, including finding an unknown side length.
- Common Core 4.MD.A.3: Use the area and perimeter formulas for rectangles in real-world and maths problems.
- Common Core 6.G.A.1: Find the area of right triangles, other triangles, special quadrilaterals and polygons by composing and decomposing shapes.
- England NC Y5.MA.ME.4: Calculate and compare the area of rectangles (including squares) in square centimetres and square metres.
- England NC Y6.MA.ME.6: Calculate the area of parallelograms and triangles.
Practice sheets
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Perimeter
Area of 2D shapes
Perimeter
1.Starter
7 minutesShow two rectangles drawn on squared paper: 6 × 2 and 4 × 3. "Which one is bigger?" Let pupils argue. Some will count the squares inside (12 and 12), some will count round the edge (16 and 14). "You're both right, but you're measuring different things. Today we sort out which is which."
2.Teach
15 minutesPerimeter. "Perimeter is the distance all the way round the edge, like a fence round a field." Trace round a 6 cm by 2 cm rectangle: 6 + 2 + 6 + 2 = 16 cm. "It's a length, so the unit is cm."
Area. "Area is the space inside a flat shape, like the grass inside the fence. We measure it in squares." Count the squares: 12. "Each square is 1 square centimetre, so the area is 12 cm²."
"Counting takes a long time for big shapes. Look: 2 rows of 6. Area of a rectangle = length × width."
Step by step
- PerimeterAdd the lengths of every side. For a rectangle: 2 × length + 2 × width.
- Area of a rectangleLength × width, in square units (cm², m²).
- Area of a right-angled triangleDraw the rectangle around it. The triangle is half: base × height ÷ 2.
Draw a 6 cm by 4 cm rectangle, then a diagonal. "Two identical triangles. Each one is half the rectangle: 24 ÷ 2 = 12 cm²." Cut a paper rectangle along its diagonal and lay the halves on top of each other to prove it.
