Idea 19of 22Builds onSame perimeter, different areas
Move a tile, change the perimeter
When you move tiles around, what changes and what stays?
Today you'll discover
- what happens to the area
- what happens to the edge
- how to count a bumpy edge
Think first12 tiles in a 4 by 3 rectangle
Move one corner tile so it sticks out at the side. What happens to the area?
Decide first, then press Next. Count the tiles, then follow the edge.
12 tiles in a 4 by 3 rectangle, 14 cm around. Then one corner tile is moved to stick out at the top right: still 12 tiles, 12 cm², but the orange edge now has eight sides adding to 16 cm. The last step shows the same 12 tiles made into a T.
See the whole ideathe big idea and the key word, in one place
The big idea
Moving tiles keeps the area the same, but the perimeter can change.
Why it happensEach tile side that touches the outside adds to the perimeter. Moving a tile out of a corner shows more of its sides.
Easy to get wrongCounting the tiles gives the area, not the perimeter. Follow the edge instead.
Key word
- rearrange
- move the same pieces into a new shape, adding none and taking none away
Ready to use it?
- Rearrange tiles and find the new perimeter.