Lesson 13 of 15
The big picture
Show on a big screenHere are all ten ideas, in order.
| Idea | Remember | Example |
|---|---|---|
| Square number | Same count across as down. | 7² = 49 |
| Odd staircase | Each new layer is the next odd number. | 16 + 9 = 25 |
| Ruling out | Squares end in 0, 1, 4, 5, 6 or 9 only. | 72 is not a square |
| Square root | The side the count came from. Check by multiplying back. | √64 = 8 |
| Pair the primes | Break, pair, keep one per pair, multiply. | 36 → 2 × 3 = 6 |
| In between | Find the square below and the square above. | 20 → between 4 and 5 |
| Cube number | A stack as deep and tall as it is wide. | 3³ = 27 |
| Cube patterns | Cubes end in every digit. Odd groups add up to cubes. | 7 + 9 + 11 = 3³ |
| Group in threes | The pairing method, in groups of three. | 2744 → 14 |
| Which count | Covering a square patch: side × side. Filling a cube-shaped space: side × side × side. | 4 units → 16 or 64 |
Chapter 1 of Part I is A Square and A Cube. Read it next and find these ideas in it.