# 5) How many significant figures are in the number 0.122210000?

If it's written just like that, it's $9$
Significant figures are just what they say. $5$ has only one, but $5.000$ has four.
This is because $5$ can be a rounded number from anywhere between $4.5 \ldots . \mathmr{and} 5.4999 \ldots$
While $5.000$ is rounded from between $4.995 \ldots \mathmr{and} 5.00499 \ldots$
The zeroes at the front don't count, so $0.0005$ still has only one significant digit.