What is 210 mm in cm? Prealgebra Ratios, Proportions, Units and Rates Metric System Unit Conversion 1 Answer EZ as pi Aug 15, 2016 #210mm div 10 = 21cm# Explanation: #10mm = 1cm# Changing to a bigger unit the number gets smaller. #210mm div 10 = 21cm# Answer link Related questions Which one is greater #5000cm.# or #5# meters? How many yards in a mile? Why is the metric system important? What is the metric system? How do you remember the metric system? How does the metric system work? How was the metric system developed? What is the conversions of grams to mL? How many ml is in 2 liters? How do you convert 1.5 kg/L to g/mL? See all questions in Metric System Unit Conversion Impact of this question 7932 views around the world You can reuse this answer Creative Commons License