# How many significant figures are in 0.04050?

Oct 1, 2017

$4$.

#### Explanation:

There are $2$ (well, perhaps $2.5$) laws of significant figures present here.

The first one being that all non-zero numbers are significant. With a $4$ and a $5$ in the number, we know there are at least $2$ significant digits.

The second being that a zero in between non-zero numbers are significant. This adds the significant digit count to $3$.

Lastly (kind of), is that a trailing zero after a decimal is significant. So the $405 \textcolor{red}{0}$ is significant. The two other zeros in front of the decimal are irrelevant.

Therefore, there are $4$ significant digits in this number.

I hope that helps!