Sometimes math can come to you at some of the most strange times. This weekend my girlfriend was cooking a pie, and had enough filling for a 13 inch crust, but we only had 9 inch pie plates. It was almost as if a math problem from a text book was coming to life. She asked me if I thought she could make a second pie from the leftover filling for the first pie, and I did some simple calculations to figure it out.
The area of a circle is (pi)*r2, so the area of a 13 inch pie is roughly 42.25*pi inches squared, since the radius is 6.5 inches (half of 13 which is a diameter). On the other hand the area of the 9 inch pie is 20.25*pi inches squared, roughly half the size of the 13 inch pie. I concluded that she did indeed have enough filling to make a second pie, and deliciousness ensued soon thereafter.