(the number of $$\rm cm$$ in $$1\rm m$$):(the number of $$\rm m$$ in $$1\rm km$$)$$=$$． 
Overseas Competition->Knowledge Point->Calculation Modules->Unit Conversion->Converting between Units of Length
$$1\rm m=100\rm cm$$ and $$1\rm km=1000m$$; the correct ratio is $$100:1000$$. 