Make 87 with four 9s

The classic four nines puzzle: build an expression from exactly four 9s that equals 87. 87 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 87 — the solver checked every possible expression.

Solutions with concatenation and decimals

Concatenation and decimals do not help for 87 either — every combination was checked.

Solutions with square roots, factorials, exponents

99 - 9 - sqrt(9) = 87
99 - sqrt(9) - 9 = 87
9 × 9 + 9 - sqrt(9) = 87
9 + 9 × 9 - sqrt(9) = 87
9 × 9 / .9 - sqrt(9) = 87

…and 40 more at this tier.

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

Make 86 with four 9s · Make 88 with four 9s

The Number Lab

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