# How do you write 500 in scientific notation?

You keep the same number of significant figures as in the original number. So, it is $5 \times {10}^{2}$. We know nothing more than one significant figure.
If it was $500.$, then we would write it as $5.00 \times {10}^{2}$. If it was $500.0$, then we would write it as $5.000 \times {10}^{2}$.