Move exactly one match to make it true.
You may not remove matches or add new ones.
💡 Hint
A plus sign cannot reach 8 here, so think about what the sign could become. Work out what the first number must then be, and compare it digit by digit.
Reveal answer
Move the vertical match from the plus sign into the middle of the first 0, turning it into an 8. The equation becomes 18 − 10 = 8.
Step-by-step solution
- 10 + 10 is 20, and one move cannot turn the 8 into 20, so the plus sign has to change.
- Removing the vertical match from the plus sign leaves a minus sign and one spare match.
- For a subtraction ending in − 10 = 8, the first number must be 18.
- A 0 has six sticks: everything except the middle bar. An 8 has all seven. Lay the spare match horizontally in the middle of the first 0 and 10 becomes 18.
- The equation now reads 18 − 10 = 8, which is true. A computer search confirmed this is the only single move that works.
Why it fools people
The size of the error is the trick. Ten plus ten versus eight feels like a gap far too large for one match, so people assume the puzzle requires something exotic. In fact the fix is the same small idea seen in easier puzzles, the plus sign giving up a stick, applied to a two-digit number. The 0 and the 8 also look so different that few people notice they differ by a single bar.
Did you get it?
About This Puzzle
Two-digit numbers change the feel of a matchstick puzzle. There are more digits on the table, more places a match could go and more ways to talk yourself into a dead end. Here the equation claims that 10 plus 10 makes 8, which is off by a mile. One match is all you get to move, and the digits are drawn in the seven-bar style you know from digital clocks. The good news is that a big error does not always need a big fix. Sometimes the right single move changes the meaning of the whole line at once.
How to Think About It
First rule out the answer side. With a plus sign, the total must be 20, and the single digit 8 cannot become a two-digit number. So consider subtraction. If the sign becomes a minus, you gain one spare match, and the first number has to be exactly 8 more than the second. Write down that number, then compare it with what is on the table. Look for the digit that is closest to its target in shape, and check that it needs exactly one added stick.
Common Traps
The most common trap is trying to rescue the plus sign by changing the 8. It already holds all seven bars, so it can only lose matches, and no smaller digit makes the sum work. Another trap is fiddling with the second 10, the number right next to the sign, because it feels like the natural partner of a minus. A third is turning a 1 into a 7, which looks promising but leads to totals that never match.
Where This Puzzle Comes From
Equations made of sticks are part of a long tradition of matchstick and toothpick puzzles found in puzzle books, magazines and party games. Two-digit versions became a favorite way to raise the difficulty without changing the rules, because each extra digit multiplies the number of moves a solver might consider. The same few transformations, like 0 to 8 and plus to minus, keep reappearing in new disguises.
Try This Variation
Try a cousin: 13 + 12 = 7. Move exactly one match to make it true. Hint: once again the first number needs to grow, but a different digit does the growing.
Show the answer to the variation
Take the vertical match from the plus sign and add it to the 3 as its upper-left stick, which turns the 3 into a 9. The equation becomes 19 − 12 = 7, which is true. A computer check found no other single move.