Four Fours/13/Solutions/1

Puzzle: Four Fours: $13$

Using exactly $4$ instances of the number $4$, the task is to write an expression for $13$, using whatever arithmetical operations you consider necessary.

Solution

$13 = \dfrac {4!} {\sqrt 4} + \dfrac 4 4$

Sources

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