Use digits and the signs +, − and =. The solver tries every match in every empty spot, so if an answer exists under the rules below, it's on the list. If you'd rather work it out yourself first, the matchstick puzzles and the hardest ones are playable on this site.
The rules it follows
- Move, don't add or take away. The same number of matches is on the table before and after.
- Digits are seven segment shapes, like a digital clock. A 1 is two matches, a 7 is three, a 4 is four, 2, 3 and 5 are five, 0, 6 and 9 are six, and an 8 is seven. A 1 can stand on the left or the right of its space.
- Signs. One flat match is a minus, a flat one with an upright one is a plus, and two flat ones are an equals sign.
- A real equation. Exactly one equals sign, a number on both sides of every sign, no gap in the middle of a number, and no number that starts with a 0 unless it is 0.
There's no times or divide, and no Roman numerals. Those puzzles use different shapes, so the solver would give answers that don't match your book.
Worked examples
The classic first.
9 − 7 = 2
There's only one way. The plus loses its upright match, which becomes a minus, and the match goes onto the 5 to make a 9. Nine minus seven is two.
Some puzzles have more than one answer, and a book usually prints just one of them.
0 + 3 = 3
8 − 3 = 5
8 − 5 = 3
All three are fair. If a puzzle tells you there's one answer, it's worth checking.
And some need two matches. Moving one match can't fix 0 + 4 = 9, but two can.
0 + 3 = 3
0 + 5 = 5
How it searches
For one move, the solver lifts each match in turn and puts it in each empty spot, then checks if the result is a true equation. In 5 + 7 = 2 there are 17 matches, so that's 170 tries, and only one of them works. For two moves it tries every pair of matches against every pair of empty spots, which is many more. On a long equation that can take a second.
The rules are the ones the Matchstick Puzzle app uses to check your answer. The app doesn't compare your move with a stored answer. It checks the equation you made, so any correct figure counts.
Questions
Can it solve two match puzzles?
Yes. Pick two matches in the Move box. The list then shows every true equation that moving exactly two matches makes, and each answer says which two matches go where.
Why isn't my book's answer on the list?
Usually the book uses a different shape for a digit, like a 7 made of four matches or a 1 made of one, or it allows something these rules don't, like turning the whole page upside down. Check the rules above against your book.
Does it do times and divide?
No. It works with plus, minus and equals, which is what most matchstick equation puzzles use.
Can it solve add a match or remove a match puzzles?
Not yet. The Matchstick Puzzle app has add and remove levels too, and shape puzzles, like leaving exactly 6 triangles.
Matchstick Puzzle
550 levels of move one, move two, add or remove and shape puzzles, and any correct answer counts.