Make 18 with four 9s

The classic four nines puzzle: build an expression from exactly four 9s that equals 18. 18 can be made with nothing but four 9s, + - × ÷, and parentheses.

Solutions using only + - × ÷

9 + 9 × 9 / 9 = 18
9 + 9 + 9 - 9 = 18
(9 + 9) × 9 / 9 = 18
(9 + 9) / 9 × 9 = 18
9 × (9 + 9) / 9 = 18

…and 6 more at this tier.

Solutions with concatenation and decimals

99 - 9 × 9 = 18
.9 × 9 + 9.9 = 18
9 + 9.9 - .9 = 18
9 - .9 + 9.9 = 18
.9 × 9 + .9 + 9 = 18

…and 29 more at this tier.

Solutions with square roots, factorials, exponents

9! + 9 + 9 - 9! = 18
9! - 9! + 9 + 9 = 18
9 + 9! × 9 / 9! = 18
9 + 9! + 9 - 9! = 18
9 + 9 × 9! / 9! = 18

…and 1252 more at this tier.

1302 distinct solutions found in total, after removing trivial rearrangements.

Make 17 with four 9s · Make 19 with four 9s

The Number Lab

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

Four Nines — the daily puzzle
Four Nines solver — every target, solved
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Four Fours solver — including the impossible five
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Today's 24 — one new hand a day

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