Four Fours/31/Solutions/1

Puzzle: Four Fours: $31$

Using exactly $4$ instances of the number $4$, the task is to write an expression for $31$, using whatever arithmetical operations you consider necessary.

Solution

$31 = 4! + 4 + \sqrt {\dfrac 4 {. \dot 4} }$

Sources

• 1964: L.H. Clarke: Fun with Figures ... (previous) ... (next): Solutions: $(46)$
• 1980: Angela Dunn: Mathematical Bafflers (revised ed.) ... (previous) ... (next): $1$. Say it with Letters: Algebraic Amusements: Four Fours