Lesson 4 of 15
Five names and what each one demands
Show on a big screenTwo tiles look alike until you measure them. How do you name a four-sided shape?
Step 1 of 4
- A shape, tilted, sides marked equal.
- Opposite sides parallel? Yes.
- All four corners 90°? No.
- All four sides equal? Yes. Best name: rhombus.
Check the shape against each name's list of demands.
Rule: A name is a list. A shape has that name only when it meets the whole list. Opposite sides are two sides that do not touch.
| Name | What it demands |
|---|---|
| Trapezium | At least one pair of parallel sides. |
| Parallelogram | Both pairs of opposite sides parallel. |
| Rectangle | Both pairs parallel, and all four corners exactly 90°. |
| Rhombus | Both pairs parallel, and all four sides the same length. |
| Square | Both pairs parallel, all four corners 90°, and all four sides equal. |
A shape can meet more than one list. Take the longest list it meets, the one with the most demands. That is its best name. A square meets all five, so its best name is square.
Watch out!
Tilting a shape onto a corner does not make it a rhombus. Measure the sides first. A tilted square is still a square.
Look at the shape. Tap its best name.
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Try the lab to finish this lesson.