Idea 14of 22Builds onA triangle's height can land outside it
Any side can be the base
Does a triangle have to stand on its bottom side?
Today you'll discover
- what changes when you turn a triangle
- which height goes with which base
- why the area stays
Think firstBase 4 cm, height 3 cm
Stand the same triangle on its 3 cm side. What is its area then?
Decide first, then press Next. For each base, find the height that meets it at a square corner.
A right triangle on a grid with base 4 cm and height 3 cm: 4 × 3 ÷ 2 = 6 cm². The same triangle is then shown using its 3 cm side as the base, with a height of 4 cm running across to it: 3 × 4 ÷ 2 = 6 cm². The last step shows a triangle pointing down, its 6 cm base along the top.
See the whole ideathe big idea and the key word, in one place
The big idea
Any side of a triangle can be its base, if the height is measured to that side.
Easy to get wrongPair each base with its own height. The 4 cm base goes with the 3 cm height; the 3 cm base goes with the 4 cm height.
Right trianglesIn a right triangle, the two sides at the square corner are already a base and a height. Multiply them and halve.
Key word
- right triangle
- a triangle with one square corner, a right angle
Ready to use it?
- Find a triangle's area using any side as the base.