A pie is removed from a 375°F oven and cools to 215°F after 15 minutes in a room at 72°F. How long (from the time it is removed from the oven) will it take the pie to cool to 72°F?
It will take at lease
Newton's Law of Cooling states that the rate of cooling of an object is inversely proportional to the difference of temperatures between the object and its surroundings i.e.
This gives us
With this it will take infinite time for object to cool down to room temperature, when
If pie cools to
Hence, it will take at lease