100 using Four 9s/Solution 2

Puzzle

It is required to express $100$ by four $9$s.

Solution

$100 = \paren {9 + .\dot 9} \paren {9 + .\dot 9}$

where $.\dot 9$ is interpreted to mean point $9$ recurring:

$.\dot 9 := .9999 \ldots = 1$