You're asking about converting millimeters (mm) to centimeters (cm). Here's the breakdown:

* 1 centimeter (cm) is equal to 10 millimeters (mm).

Therefore, to convert millimeters to centimeters, you divide the number of millimeters by 10.

For example:

* 20 mm = 20 / 10 = 2 cm

* 50 mm = 50 / 10 = 5 cm

So, the fraction to represent mm in terms of cm is 1/10.