Idea 2of 22Builds onArea counts the squares inside
Perimeter is the distance around
How far is it all the way around a shape?
Today you'll discover
- how to walk the edge of a shape
- how to add the sides
- how it differs from area
Think firstThe same rectangle: 5 cm long, 3 cm wide
An ant walks once around the edge. How far does it walk?
Decide first, then press Next. Follow the edge all the way round.
The 5 by 3 rectangle with its sides marked 5 cm, 3 cm, 5 cm and 3 cm. A thick orange line draws itself around the edge, and a line under it adds 5 + 3 + 5 + 3 = 16 cm. Then the squares come back and both lines show: area 15 cm², perimeter 16 cm. The last step shows a 7 by 4 rectangle.
See the whole ideathe big idea and the key word, in one place
The big idea
Perimeter is the distance all the way around a shape: add every side.
Compare themArea counts the squares inside: 15 cm². Perimeter measures the length around the edge: 16 cm. They are two different measures of one shape.
Easy to get wrongWalk every side once. Stopping after two sides gives only half the perimeter.
Key word
- perimeter
- the total distance around the outside of a shape
Ready to use it?
- Find the perimeter of a rectangle by adding its sides.