The Luchins water jar problem
Given a 21-cup jar, a 127-cup jar, and a 3-cup jar, measure out exactly 100 cups
Given a 14-cup jar, a 46-cup jar, and a 5-cup jar, measure out exactly 22 cups
Given an 18-cup jar, a 43-cup jar, and a 10-cup jar, measure out exactly 5 cups
Given a 15-cup jar, a 39-cup jar, and a 3-cup jar, measure out exactly 18 cups