Four Fours/90

Puzzle

Using exactly $4$ instances of the number $4$, the task is to write an expression for $90$, using whatever arithmetical operations you consider necessary.

Solutions

Solution $1$

$90 = \dfrac 4 {.4} \times \dfrac 4 {. \dot 4}$

Solution $2$

$90 = \dfrac {4 \times 4} {.4 \times {.\dot 4} }$

Solution $3$

$90 = 4 \times 4! - 4 - \sqrt 4$

Also see

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