A comb for horses has $$100$$ teeth (the width of the teeth are negligible). The distance between the $$4$$\textsuperscript{th}~teeth and the $$9$$\textsuperscript{th}~teeth is $30$ mm. How long is the comb in centimetres? 
Overseas Competition->Knowledge Point->Word Problem Modules->Interval Problems->Straight Line Type with Objects on Both Sides->Planting Trees on Both Sides