There are 10mm in a cm. Therefore you have to multiply by 10 to get the answer. 20cm x 10 is 200mm.
if you have 100 millimetres, you have 10 centimetres. 200mm is 20cm, and so on. this is because there are 10mm in every cm
it is 200mm
200mm = 20cm
200mm is 0.2m
20cm is 200mm
If you mean how many mm in 20cm then there are 200mm