How does the matchstick puzzle work?
Each puzzle is a wrong sum or subtraction made of matches, like 6 + 4 = 4. Tap a match to lift it, then tap an empty place to lay it there. If the equation is now true, it is fixed; if not, put the match back and try again. The equals sign and the minus bar stay put, but the upright of a plus can move. There are 5 puzzles.
Every puzzle is made from a true equation by moving one match, so it always has a fix, and the game accepts any fix that works. Puzzles are kept only if they have one to three fixes, which the site's tests check.
How is your result calculated?
Your result is how many of the 5 equations you fixed, with your time over the whole set and the number of moves that didn't work. "Show me" reveals one fix and counts that puzzle as shown, not fixed.
Which digits can one match change?
Digits are drawn like a digital clock, from up to seven matches. Moving one match inside a digit, adding one or taking one away turns it into the digits below. The table is worked out by the puzzle's own code from the shapes it draws.
| Digit | Matches | Move one inside | Add one | Take one away |
|---|---|---|---|---|
| 0 | 6 | 6, 9 | 8 | – |
| 1 | 2 | – | 7 | – |
| 2 | 5 | 3 | – | – |
| 3 | 5 | 2, 5 | 9 | – |
| 4 | 4 | – | – | – |
| 5 | 5 | 3 | 6, 9 | – |
| 6 | 6 | 0, 9 | 8 | 5 |
| 7 | 3 | – | – | 1 |
| 8 | 7 | – | – | 0, 6, 9 |
| 9 | 6 | 0, 6 | 8 | 3, 5 |
The operator changes too: taking the upright from a plus leaves a minus, and laying one on a minus makes a plus.
How to solve matchstick puzzles
- Try the sign first. Swapping plus and minus is one move, and it is easy to miss.
- Balance the matches. One move keeps the total, so if one digit gains a match, another must lose one, unless the match moves inside a single digit.
- Look at 9s and 6s. They change the most ways: one match turns a 9 into 0, 3, 5, 6 or 8, and a 6 into 0, 5, 8 or 9.
For more number puzzles, try Make 24 or the Number Sequence Test.