Parallelogram area
Area = base x perpendicular height.
Use the perpendicular height, not the sloping side.
Year 6
Calculate the area of parallelograms and triangles
Use the correct area formula for parallelograms and triangles.
Lesson overview
Measurement
A parallelogram uses base x perpendicular height. A triangle uses half of base x perpendicular height because two matching triangles can make a parallelogram.
Triangle area
Area = 1/2 x base x height.
A triangle is half the matching parallelogram.
Worked example
Find the area of a triangle with base 10 cm and height 6 cm.
| Base | Height | Area |
|---|---|---|
| 10 | 6 | 30 cm² |
- Multiply base by height: 10 x 6 = 60.
- Take half of 60.
- Half of 60 is 30.
- So the area is 30 square centimetres.
Try it
Pick the correct formula before you start calculating.
Question 1
The area of a parallelogram with base 8 cm and height 5 cm is:
Question 2
The area of a triangle with base 10 cm and height 6 cm is:
Question 3
Which height should be used?
Question 4
A triangle is half of which related shape?
Question 5
A parallelogram with base 12 cm and height 4 cm has area:
Common mistakes
Watch for these when working through the lesson.
- Using the sloping side instead of the perpendicular height.
- Forgetting to halve the area for a triangle.
- Mixing area formulas with perimeter ideas.
Related topics
These ideas fit closely with this lesson.
- Recognise when it is possible to use formulae for area and volume.
- Recognise that shapes with the same areas can have different perimeters.