Idea 10of 22Builds onLength × width gives the area
A parallelogram becomes a rectangle
How can a leaning shape have the same area as a rectangle?
Today you'll discover
- where to cut the leaning shape
- where the piece goes
- the rule for its area
Think firstA leaning shape with two pairs of parallel sides
Cut a triangle off one end and slide it to the other end. What shape do you get?
Decide first, then press Next. Watch where the orange piece goes.
A parallelogram on a grid, base 6 cm along the bottom and slanted sides of 5 cm. A dashed blue line drops straight from the top left corner to the base: height 4 cm. The orange triangle to its left is cut off, then slides 6 squares to the right, closing a rectangle 6 cm by 4 cm, and the line base × height = 6 × 4 = 24 cm² appears. The last step shows a parallelogram with base 5 m and height 4 m.
See the whole ideathe big idea and the key word, in one place
The big idea
A parallelogram can be cut and slid into a rectangle, so its area is base × height.
Why it happensCutting and sliding moves squares without adding or losing any, so the rectangle and the parallelogram cover the same area.
For exampleBase 6 cm, height 4 cm: 6 × 4 = 24 cm², the same as a 6 cm by 4 cm rectangle.
Key words
- parallelogram
- a four-sided shape whose opposite sides are parallel: they run side by side and never meet
- base
- the side a shape stands on, used with the height to find its area
Ready to use it?
- Find the area of a parallelogram with base × height.