100 using Four 9s/Solution 1

Puzzle

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

Solution

$100 = 99 \frac 9 9$

Sources

• 1821: John Jackson: Rational Amusement for Winter Evenings
• 1992: David Wells: Curious and Interesting Puzzles ... (previous) ... (next): Rational Amusements for Winter Evenings: $146$