Make 5 with four 9s

The classic four nines puzzle: build an expression from exactly four 9s that equals 5. 5 cannot be made with + - × ÷, concatenation, or decimals (the solver checked every expression) — solutions need square roots, factorials, or exponents.

Solutions using only + - × ÷

No expression made of four plain 9s and + - × ÷ reaches 5 — the solver checked every possible expression.

Solutions with concatenation and decimals

Concatenation and decimals do not help for 5 either — every combination was checked.

Solutions with square roots, factorials, exponents

9 - 9 / 9 - sqrt(9) = 5
9 - sqrt(9) - 9 / 9 = 5
99 / 9 - sqrt(9)! = 5
(9 + 9) / 9 + sqrt(9) = 5
(9 / .9)! / (9! + 9!) = 5

…and 616 more at this tier.

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

Make 4 with four 9s · Make 6 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.