Idea 7of 22Builds onLength × width gives the area
Split a shape into rectangles
How do you find the area of an L-shaped floor?
Today you'll discover
- where to cut the shape
- how to add the parts
- a second way: take away the corner
Think firstAn L-shaped floor, with every side marked
What is the area of this L-shaped floor?
Decide first, then press Next. Find where to cut the shape into rectangles.
An L-shaped floor on a grid, sides 4 m, 3 m, 4 m, 2 m, 8 m and 5 m. A dashed line cuts it into a 4 by 5 rectangle marked 20 and a 4 by 2 rectangle marked 8, and the line Area: 4 × 5 + 4 × 2 = 20 + 8 = 28 m² appears. The last step shows an L-shaped yard.
See the whole ideathe big idea and the key word, in one place
The big idea
Split a shape made of rectangles into rectangles, find each area, then add them.
Or take awayThe whole 8 m by 5 m box is 40 m². Take away the empty 4 m by 3 m corner, 12 m², and 28 m² is left.
Easy to get wrongDon't multiply the two longest sides. 8 × 5 = 40 counts the empty corner as floor too.
Key word
- composite shape
- a shape made by putting simpler shapes together, like two rectangles making an L
Ready to use it?
- Find the area of a shape made of two rectangles.