If $2\text{cm}$ represents $50\text{km}$ on a map and the distance between two towns on this map is $7.5\text{cm}$, then their actual distance apart is ． 
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If $$2\textasciitilde\text{cm}$$ represents $$50\textasciitilde\text{km}$$, $$1\textasciitilde\text{cm}$$ represents $$25\textasciitilde\text{km}$$. So, their actual distance apart is $$7.5\times 25=187.5\textasciitilde\text{km}$$. 