Area of a triangle
The Maths Habit
1 How many squares cover the rectangle?
152 Work out the area of the rectangle.
28 cm23 What is half of 36?
18
A rectangle is cut from corner to corner. Which piece is bigger, A or B?
Neither. A turned round fits on B. Each is half.
- Area
- The space inside a flat shape.
- Base
- The side the shape sits on.
- Perpendicular height
- How tall the shape is, measured at a right angle to the base.
- Right angle
- A square corner. It is a quarter turn.
- Find the rectangle.Base × height.
- The triangle is half the rectangle.Divide by 2.
- Write the units.Area is in square units: cm².
Work out the area.
Work out the area.
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Work out the area.
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Work out the area.
Work out the area of each triangle.
Which line is the perpendicular height?
Which line is the perpendicular height?
- The height is the dashed line.It meets the base at a right angle.
- The two striped pieces fit inside the triangle.So the triangle is still half the rectangle.
- Use the same frame.Rectangle, half, area.
Work out the area.
Work out the area.
Work out the area.
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Work out the area.
Work out the area.
Work out the area.
Work out the area of each triangle.
Is the area right? Thumbs up or thumbs down.
Answer sheet
Two right angled triangles fit together to make a rectangle 8 cm by 5 cm. What is the area of one triangle?
20 cm2A triangle has an area of 15 cm². Its base is 5 cm. How tall is it?
6 cmA house shape is a square 6 cm by 6 cm with a triangle roof 4 cm tall on top. Work out its area.
48 cm2
Work out the area of the triangle. Rectangle7×4=28Half28÷ 2 =14
Area = 14 cm2Work out the area of the triangle. Rectangle10×5=50Half50÷ 2 =25
Area = 25 cm2Work out the area of the triangle.
35 cm2