Idea 5of 22Builds onPerimeter is the distance aroundLength × width gives the area
Two lengths and two widths
Do you need to measure all four sides of a rectangle?
Today you'll discover
- which sides of a rectangle match
- a shortcut for the perimeter
- how a square is different
Think firstThe top is 9 cm. One side is 6 cm.
You measured the top and one side. Do you know the other two sides?
Decide first, then press Next. Compare each side with the side across from it.
A 9 by 6 rectangle on a grid with no lengths shown; then its sides marked 9 cm, 6 cm, 9 cm and 6 cm. An orange line goes round it and the line 9 + 6 + 9 + 6 = 30 cm appears, then half way round: 9 + 6 = 15 cm. The last step shows an 8 m by 3 m rectangle.
See the whole ideathe big idea and the key word, in one place
The big idea
A rectangle's opposite sides are equal, so its perimeter is two lengths plus two widths.
Half way, then double
Add one length and one width to get half way round, then double it.
- length9 cm
- width6 cm
- half way15 cm
- perimeter30 cm
Easy to get wrongDon't stop at half way. 9 + 6 covers only two of the four sides.
Key word
- opposite sides
- two sides of a shape that face each other across it
Ready to use it?
- Find a rectangle's perimeter from its length and width.