Make 89 with four 9s

The classic four nines puzzle: build an expression from exactly four 9s that equals 89. 89 cannot be made with + - × ÷ alone (the solver checked every expression) — you will need to stick 9s together (like 99) or use decimals (like .9).

Solutions using only + - × ÷

No expression made of four plain 9s and + - × ÷ reaches 89 — the solver checked every possible expression.

Solutions with concatenation and decimals

99 - 9 / .9 = 89
(9 × 9 - .9) / .9 = 89

Solutions with square roots, factorials, exponents

(9 - sqrt(9))! / 9 + 9 = 89
(9 × 9 + sqrt(9)!!) / 9 = 89
(9 / sqrt(9))!! / 9 + 9 = 89
(9 - sqrt(9)!)!! / 9 + 9 = 89
(.9 + sqrt(9)!!) / .9 / 9 = 89

…and 22 more at this tier.

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

Make 88 with four 9s · Make 90 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.