First let's convert all of these into centimeters using the correct conversions:
[tex] 7cm=7cm [/tex]
[tex] (\frac{18mm}{1})* (\frac{1cm}{10mm})=1.8cm [/tex]
[tex] (\frac{1m}{1}) *(\frac{100cm}{1m})=100cm [/tex]
[tex] (\frac{3dm}{1})* (\frac{10cm}{1dm})=30cm [/tex]
Therefore we can rank them in order now:
18mm < 7 cm < 3 dm < 1 m
