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A cup of boiling water ($212$\textsuperscript{◦}F) is placed to cool in a room whose temper- ature remains constant at $68$\textsuperscript{◦}F. Suppose the difference between the water temperature and the room temperature is halved every $5$ minutes. What is the water temperature, in degrees Fahrenheit, after $15$ minutes? 
Overseas Competition->Knowledge Point->Calculation Modules
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