Final answer:
Rulers with millimeter markings are more precise for measuring lengths compared to rulers with only centimeter markings.
Step-by-step explanation:
When measuring with a ruler, we need to consider the precision of the ruler markings. For example, if the ruler has only centimeter markings, the measurement will be less precise compared to a ruler with millimeter markings. The more digits reported in a measurement, the more precise it is. The tenths digit is uncertain when measuring with centimeter markings, while it can be estimated when measuring with millimeter markings. Therefore, the ruler with millimeter markings is more precise for measuring lengths.