Watch: Calculating the area of triangles
TRIANGLE: I'm a triangle! Of course I am, obviously, you knew that. I've got 3 sides. And this is rectangle.
You're supposed to say hello rectangle…
RECTANGLE: Hi.
TRIANGLE: Now you may well be asking yourself how do we find the area of triangle? Well it's simple really, because there are always 2 of me in rectangle. Look…
RECTANGLE: Ow, get off…
TRIANGLE: So you find the area of rectangle, and then divide it by 2, and that's my area. And it works no matter what size and shape I am. Look… now I'm 4 cm high and 3 cm wide! If rectangle changes shape too…
RECTANGLE: I don't want to.
TRIANGLE: You have to! That's the whole point!
RECTANGLE: It's embarrassing.
TRIANGLE: Go on!
RECTANGLE: Unnh
TRIANGLE: Now he's 4 cm high and 3 cm wide, like me. He's 12 square cm, so I must be half that… 6 square centimetres! And whatever shape I am it still works!
RECTANGLE: You're just really embarrassing. I want to go home.
How do you calculate the area of a triangle?
To calculate the area of a triangle, multiply the height by the width (this is also known as the 'base') then divide by 2.
Can you find the area of a triangle where height = 5 cm and width = 8 cm?
5 × 8 = 40 ÷ 2 = 20
The area is 20cm².
Activity 1
Activity 2
Primary maths teaching resources
Visit BBC Bitesize for Teachers to see videos, activities and more resources to use in maths classes for KS1 and KS2.
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