Make 80 with four 9s

The classic four nines puzzle: build an expression from exactly four 9s that equals 80. 80 can be made with nothing but four 9s, + - × ÷, and parentheses.

Solutions using only + - × ÷

9 × 9 - 9 / 9 = 80

Solutions with concatenation and decimals

9 × 9 - .9 / .9 = 80
(9 × 9 - 9) / .9 = 80

Solutions with square roots, factorials, exponents

9 × 9 - 9! / 9! = 80
9 × 9 - (9 - 9)! = 80
9 × 9 - (.9 - .9)! = 80
9 × 9 - (9! - 9!)! = 80
(9 ^ sqrt(9) - 9) / 9 = 80

…and 703 more at this tier.

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

How 80 compares

80 has 711 distinct solutions across all three tiers — #16 most plentiful of all 100 targets. Exactly one of them uses nothing but + - × ÷. Next door, 79 has 34 solutions and 81 has 738 solutions.

If 80 went down easily, make 79 with four 9s — 34 solutions, the nearest step up in scarcity.

Make 79 with four 9s · Make 81 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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Stay for something you did not search for.

Four Nines — the daily puzzle: four 9s, one target, new at midnight
The Reflex Lab — nine ways to measure your hands and memory, none of them polite about it
hand me something weird — a random pick from the directory. Could be the horse.

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