Four Fours/20/Solutions/4

Puzzle: Four Fours: $20$

Using exactly $4$ instances of the number $4$, the task is to write an expression for $20$, using whatever arithmetical operations you consider necessary.

Solution

$20 = \dfrac {4! \times 4} 4 - 4$

Sources

• 1980: Angela Dunn: Mathematical Bafflers (revised ed.) ... (previous) ... (next): $1$. Say it with Letters: Algebraic Amusements: Four Fours