If an object is 100 millimeters in length how many centimeters is it?

Answer: 10 centimeters

To answer this question you need to understand the metric system scale. In metric system 1 centimeter is equal to 10 millimeters or 1/100 meter. This means the equation looks like

1 centimeter = 10 millimeter

After that, you only need to convert the unit. Then 100 millimeters would be:

100 millimeter x 1centimeter / 10 millimeter = 10 centimeters.