This Application Problem is a part of the Lesson 20, Unit 4, Grade 2.<br> In this lesson, students continue to apply their understanding of place-value strategies for addition as they move from concrete to pictorial as they use math drawings to represent compositions of 1 ten and 1 hundred. Students relate their drawings to the vertical form, recording each change they make to their model on the numerical representation. They use place-value language to explain these changes.