In this lesson, students measure and compare sets of three items using centimeter cubes and use their measurements to make comparative statements about length. For example, "The pencil measures 10 centimeters. The crayon measures 6 centimeters. The book measures 20 centimeters. The order from shortest to longest is the crayon, the pencil, and the book. The book is longer than the pencil, and the pencil is longer than the crayon, so the book is longer than the crayon." Students also solve "compare with difference unknown" word problems, determining how much longer a given object is than another.