The big picture
The same digits can make very different numbers.
| Idea | Remember |
|---|---|
| Rearranging digits | Same digits, new order, new number. |
| Biggest and smallest | Biggest digit first for biggest. Smallest digit that is not 0 first for smallest. |
| Palindromes | Reads the same both ways. Reverse and add to reach one. |
| Supercells | Bigger than every neighbour it has. |
| Estimation | Round the real numbers, then add. |
| Number puzzles | Each clue crosses out numbers. |
| 6174 | Biggest minus smallest. Repeat. Four digits that are not all the same end at 6174. |
| Collatz | Even: halve. Odd: times 3, add 1. Repeat to reach 1. |
| Number games | Work backwards. Winning numbers are 4 apart. |
Open Chapter 3, Number Play. You have played these games already.