Lesson 8 of 15
A cube number counts real cubes
Show on a big screenA sweet shop cuts barfi into cubes. A box holds 3 cubes across, 3 deep and 3 high.
Step 1 of 4
- Layer 1: a 3 × 3 flat layer, 9 cubes.
- Layer 2 on top: 9 more.
- Layer 3 on top of that: 9 more.
- 9 + 9 + 9 = 27 = 3³.
Rule: Stack layers with no gaps. Go as deep as the block is wide. That count is a cube number.
3 × 3 × 3 is written 3³. We say three cubed. The small raised 3 says three 3s are multiplied.
A unit cube is a small cube, 1 unit along each edge.
| Edge | Written | Unit cubes |
|---|---|---|
| 1 | 1³ | 1 |
| 2 | 2³ | 8 |
| 3 | 3³ | 27 |
| 4 | 4³ | 64 |
| 5 | 5³ | 125 |
| 6 | 6³ | 216 |
| 7 | 7³ | 343 |
| 8 | 8³ | 512 |
| 9 | 9³ | 729 |
| 10 | 10³ | 1000 |
A drawing shows three faces at most. So some unit cubes are hidden. A 3 by 3 by 3 cube holds 27 unit cubes. Only the one in the middle touches no outside face.
Watch out!
"4³ means 4 × 3, so it is 12" is wrong. The raised 3 says three 4s are multiplied. 4 × 4 × 4 = 64.
Tap Add a layer. Then tap Next size.
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Try the lab to finish this lesson.