# What is the length of the nail reported to the correct num ber of significant figures?

The measurement should be $\text{5.75 cm}$ with three significant figures.
When measuring, you record the units that you can definitely read, plus one estimated digit. In this case, the nail is definitely at least $\text{5.5 cm}$. However, it is in between $\text{5.5 cm}$ and $\text{6.0 cm}$. It looks like it's in the middle between $\text{5.5 cm}$ and $\text{6.0 cm}$. Half of $\text{0.5 cm}$ is $\text{0.25 cm}$. So the measurement to the correct number of significant digits should be read as: $\text{5.5 cm + 0.25 cm = 5.75 cm}$.