Lesson 1 of 11
When a square is only half covered
Show on a big screenA slanted edge cuts through some squares. What does each cut square count as? Each square is 1 cm by 1 cm. Its size is 1 cm², one square centimetre.
Step 1 of 4
- A right triangle, 6 across and 4 up.
- 8 squares are fully inside: 8 cm².
- 8 more are only part covered, holding 4 cm² between them.
- Whole plus part: 8 + 4 = 12 cm².
Area — the number of unit squares a shape covers.
A part square is not a zero, and not a one
A part square is one the shape covers only partly. It counts as the part it holds. A square half covered counts as half. It does not count as nothing. It does not count as a whole one.
Two quick checks give limits for the answer. Count whole squares only: 8, too small. Count every square the shape touches: 16, too big. The is 8 + 4 = 12.
Look at the grid. Tap the .
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