Make 70 with four 9s

The classic four nines puzzle: build an expression from exactly four 9s that equals 70. 70 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 70 — the solver checked every possible expression.

Solutions with concatenation and decimals

Concatenation and decimals do not help for 70 either — every combination was checked.

Solutions with square roots, factorials, exponents

sqrt(9)!! / 9 - 9 / .9 = 70
(9 + 9 × sqrt(9)!) / .9 = 70
(sqrt(9)!! - 9) / 9 - 9 = 70
9! × 9 / sqrt(9)! ^ sqrt(9)! = 70
9 × 9! / sqrt(9)! ^ sqrt(9)! = 70

…and 6 more at this tier.

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

How 70 compares

70 has 11 distinct solutions across all three tiers — #25 scarcest of all 100 targets. Next door, 69 has 34 solutions and 71 has 30 solutions.

If 70 went down easily, make 68 with four 9s — 5 solutions, the nearest step up in scarcity.

Make 69 with four 9s · Make 71 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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