Make 25 with four 9s

The classic four nines puzzle: build an expression from exactly four 9s that equals 25. 25 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 25 — the solver checked every possible expression.

Solutions with concatenation and decimals

Concatenation and decimals do not help for 25 either — every combination was checked.

Solutions with square roots, factorials, exponents

9 + 9 / .9 + sqrt(9)! = 25
9 + sqrt(9)! + 9 / .9 = 25
(9 × 9 - sqrt(9)!) / sqrt(9) = 25
(9 + sqrt(9)! ^ sqrt(9)) / 9 = 25
(9 - sqrt(9)! / 9) × sqrt(9) = 25

…and 7 more at this tier.

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

How 25 compares

25 has 12 distinct solutions across all three tiers — #28 scarcest of all 100 targets. Next door, 24 has 1,116 solutions and 26 has 89 solutions.

If 25 went down easily, make 32 with four 9s — 3 solutions, the nearest step up in scarcity.

Make 24 with four 9s · Make 26 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
Four Fours — the 1881 original
Four Fours solver — including the impossible five
Make 24 solver — any four digits
Today's 24 — one new hand a day

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Four Nines — the daily puzzle: four 9s, one target, new at midnight
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hand me something weird — a random pick from the directory. Could be the horse.

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