Make 10 with four 9s

The classic four nines puzzle: build an expression from exactly four 9s that equals 10. 10 can be made with nothing but four 9s, + - × ÷, and parentheses.

Solutions using only + - × ÷

(9 + 9 × 9) / 9 = 10

Solutions with concatenation and decimals

99 / 9.9 = 10
9.9 / .99 = 10
(99 - 9) / 9 = 10
.9 / 9 + 9.9 = 10
9 × 9 / .9 / 9 = 10

…and 59 more at this tier.

Solutions with square roots, factorials, exponents

(9 / 9) ^ 9 + 9 = 10
9 + 9 ^ (9 - 9) = 10
(9 - 9)! ^ 9 + 9 = 10
.9 ^ (9 - 9) + 9 = 10
9! × 9 / .9 / 9! = 10

…and 733 more at this tier.

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

Make 9 with four 9s · Make 11 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

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