This Application Problem is a part of the Lesson 18, Unit 6, Grade 2.<br> In this lesson, students pair up to 20 objects and see that, when objects are paired with none remaining, the number is even. They see that objects arranged in columns of two also create two equal groups. For example, a 2-by-7 array may be seen as 7 columns of 2 or 2 rows of 7.