# Differential Equations

### Exercises

#### Exercise 10

A hot cup of coffee is placed on the kitchen table in a room that is 68°F. Newton's Law of Cooling (link forward) says that the temperature *t* of the coffee will decrease at a rate proportional to the difference between the temperature of the surrounding room and the temperature of the coffee. This situation can be modeled by the differential equation

Is the constant *k* positive or negative?

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