Write 89.99 in scientific notation.
\[
\begin{aligned}
89.99 & =\frac{8999}{100} \\
& =\frac{8999}{10^{2}} \\
& =8999 \times 10^{-2} \\
& =\left(8999 \times \frac{1000}{1000}\right) \times 10^{-2} \\
& =(8.999 \times 1000) \times 10^{-2} \\
& =8.999 \times 10^{3} \times 10^{-2} \\
& =8.999 \times 10^{3-2}
\end{aligned}
\]
