Title: An Entertaining Puzzle Speaker: J Moore Abstract: Suppose you are given two bottles, one measuring exactly 5 gallons and the other exactly 3. Can you measure out exactly 1 gallon? Generalize the problem to two bottles of arbitrary size. Can you measure out 1 gallon? In this talk I will describe how I formalized this problem in ACL2 and proved several interesting theorems about ``the bottle problem.''