Make 9 with four 9s

The classic four nines puzzle: build an expression from exactly four 9s that equals 9. 9 can be made with nothing but four 9s, + - × ÷, and parentheses.

Solutions using only + - × ÷

(9 - 9) / 9 + 9 = 9
9 + 9 × (9 - 9) = 9
9 - (9 - 9) / 9 = 9
9 - 9 × (9 - 9) = 9

Solutions with concatenation and decimals

9 / .9 - 9 / 9 = 9
(9 - 9) / .9 + 9 = 9
.9 × (9 + 9 / 9) = 9
.9 × (9 - 9) + 9 = 9
9 × (9 / .9 - 9) = 9

…and 17 more at this tier.

Solutions with square roots, factorials, exponents

(9 - 9) ^ 9 + 9 = 9
(9 / 9) ^ 9 × 9 = 9
9 × 9 ^ (9 - 9) = 9
9 - (9 - 9) ^ 9 = 9
9 / (9 / 9) ^ 9 = 9

…and 3230 more at this tier.

3261 distinct solutions found in total, after removing trivial rearrangements.

Make 8 with four 9s · Make 10 with four 9s

The Number Lab

Same idea, different constraints: four 9s, four 4s, or any four digits you like.

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Play the daily Four Nines puzzle, pick another number in the solver, or find more free math games.