burger fun / Four Fours / Solver

Make 78 with four 4s

The classic four fours puzzle: build an expression from exactly four 4s that equals 78. 78 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 4s and + - × ÷ reaches 78 — the solver checked every possible expression.

Solutions with concatenation and decimals

Concatenation and decimals do not help for 78 either — every combination was checked.

Solutions with square roots, factorials, exponents

• 4 × (4! - 4) - sqrt(4) = 78

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

Make 77 with four 4s · Make 79 with four 4s

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

Read up on the 1881 original, pick another number in the solver, or find more free math games.