Four Numbers Make Ten
Combine four digits (1-9), two at a time, using plus, minus, times and divide to make exactly 10. Every puzzle is checked to be solvable. A few of them need a fraction along the way.
Tap the first card
How to play
Tap one number card, choose + − × ÷, then tap another card. The two cards are replaced by one card with the result. Repeat until a single card is left, and make it 10. Division can create fractions such as 1/3; just keep using them. "Undo" takes back a step. "Hint" gives an idea, then the first two cards to combine, then the answer. "Auto-solve" shows how to make 10 from the current cards, one step at a time.
Learn more
There are 495 ways to choose four digits from 1-9 (ignoring order), and 447 of them can make 10. This was checked by enumerating every expression, and it agrees with a second, independently written checker. Some sets cannot: 1-1-1-1 and 1-1-7-7 never reach 10. Division can produce fractions. For 4 of the 495 sets (1-1-5-8, 1-1-9-9, 1-3-3-7 and 3-4-7-8) every solution passes through a fraction. Fractions can be added, subtracted, multiplied and divided exactly. Decimals would turn 1/3 into 0.333... and cause tiny errors, so this page keeps every step as an exact fraction.