Idea 22of 22Builds onTwo triangles make a parallelogramSplit a shape into rectangles
A wall with a triangle on top
How do you find the area of a wall with a pointed top?
Today you'll discover
- how to split the wall
- which part to halve
- how the edge is different
Think firstA shed wall, 8 m wide, with a pointed top
The rectangle is 8 m by 4 m; the triangle on top is 3 m tall. What is the total area?
Decide first, then press Next. Find the rectangle, then the triangle on top of it.
The front wall of a shed on a grid: an 8 m by 4 m rectangle with a triangle on top whose dashed height is 3 m. Squares fill the rectangle and the triangle is tinted orange; the line Area: 8 × 4 + 8 × 3 ÷ 2 = 32 + 12 = 44 m² appears. Then an orange line goes round the edge: 5 + 5 + 4 + 8 + 4 = 26 m. The last step shows a barn wall.
See the whole ideathe big idea and the key word, in one place
The big idea
Split a wall into a rectangle and a triangle, find each area, and add them.
Part by part
Each part has its own rule; add the parts at the end.
- rectangle8 × 4 = 32 m²
- triangle8 × 3 ÷ 2 = 12 m²
- wall44 m²
Easy to get wrongThe triangle's height is its own 3 m, from the top point down to the rectangle, not the whole 7 m from the ground.
Key word
- gable
- the triangle part at the top of a wall, under a sloping roof
Ready to use it?
- Find the area of a shape made of a rectangle and a triangle.