burger fun / Four Nines / Solver
Make 91 with four 9s
The classic four nines puzzle: build an expression from exactly four 9s that equals 91. 91 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 91 — the solver checked every possible expression.
Solutions with concatenation and decimals
9 × 9 + 9 / .9 = 91(.9 + 9 × 9) / .9 = 91
Solutions with square roots, factorials, exponents
(99 + sqrt(9)!!) / 9 = 91
3 distinct solutions found in total, after removing trivial rearrangements.
How 91 compares
91 has 3 distinct solutions across all three tiers — #8 scarcest of all 100 targets. Next door, 90 has 185 solutions and 92 has 4 solutions.
If 91 went down easily, make 94 with four 9s — just one solution, the nearest step up in scarcity.
Make 90 with four 9s · Make 92 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
Got what you came for?
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.