Make 100 with four 4s

The classic four fours puzzle: build an expression from exactly four 4s that equals 100. 100 cannot be made with + - × ÷ alone (the solver checked every expression) — you will need to stick 4s together (like 44) or use decimals (like .4).

Solutions using only + - × ÷

No expression made of four plain 4s and + - × ÷ reaches 100 — the solver checked every possible expression.

Solutions with concatenation and decimals

44 / .44 = 100
(44 - 4) / .4 = 100
4 × 4 / .4 / .4 = 100
4 / .4 × 4 / .4 = 100
4 / (.44 - .4) = 100

…and 5 more at this tier.

Solutions with square roots, factorials, exponents

4 × (4! + 4 / 4) = 100
(4! + 4 × 4) / .4 = 100
4! × (4 + 4 / 4!) = 100
(.4 / .4 + 4!) × 4 = 100
4 × (4! + 4! / 4!) = 100

…and 146 more at this tier.

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

Make 99 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.