This Problem Set is a part of the Lesson 12, Unit 4, Grade 2. In this lesson, students deepen their conceptual understanding of subtraction as they relate manipulatives to a written method, recording recompositions in vertical form. Students use a "magnifying glass" method to examine the whole minuend and determine if each digit is big enough to subtract the number below it. If not, they decompose one of the next larger units to make 10 of the unit they need.
