Joan needs $$250$$ pounds of metal with $$27\textbackslash\%$$ silver. If Joan combines one metal with $$23\textbackslash\%$$ silver, and another with $$43\textbackslash\%$$ silver,how much of each metal does Joan need respectively? 
Overseas Competition->Knowledge Point->Word Problem Modules->Solving Problems Involving Fractions and Percentages->Knowing the Base
$$\dfrac{43\textbackslash\%-27\textbackslash\%}{27\textbackslash\%-23\textbackslash\%}=\dfrac{16}{4}=\dfrac{4}{1}$$,  $$23\textbackslash\%$$ silver:$$250\times\dfrac{4}{4+1}=200$$,  $$43\textbackslash\%$$ silver:$$250\times\dfrac{4}{4+1}=50$$. 