Idea 8of 22Builds onSplit a shape into rectanglesTwo lengths and two widths
Find the missing sides first
How do you find a perimeter when some sides have no number?
Today you'll discover
- where a missing side's length hides
- how to walk all six sides
- why the L matches its box
Think firstThe L-shaped floor, with two sides not marked
How long is the short side that steps down from the top?
Decide first, then press Next. Compare each missing side with the side across from it.
The L-shaped floor with sides 4 m, a question mark, a question mark, 2 m, 8 m and 5 m. The missing sides fill in green as 3 m and 4 m, with a sentence that a missing side matches part of the side across from it. An orange line then goes round all six sides: 26 m. The last step shows the L-shaped yard.
See the whole ideathe big idea and the key word, in one place
The big idea
Find each missing side from the sides across from it, then add every side.
Across from each other
The short sides on one side of the L add up to the long side across from them.
- left side5 m
- right sides3 m + 2 m
- bottom8 m
- top sides4 m + 4 m
Easy to get wrongCount each of the six sides once. Missing one short side is the most common slip.
Key word
- missing side
- a side with no length printed, worked out from the sides you do know
Ready to use it?
- Find missing side lengths, then the perimeter of an L-shape.