Because:
[tex]\sqrt[]{100}=10[/tex]Can be written as a simple fraction:
[tex]\begin{gathered} \frac{n}{d} \\ \text{where:} \\ n\in Z \\ d\in Z,d\ne0 \end{gathered}[/tex][tex]10=\frac{10}{1}[/tex]However:
[tex]\sqrt[]{99}=3\sqrt[]{11}=9.949874371\ldots[/tex]Can be written as a simple fraction