This Problem Set is a part of the Lesson 35, Unit 1, Grade 1. In this lesson, students apply their knowledge of doubles and fives to subtraction. For example, when presented with 8 - 5, students learn to think of the decomposition of 8 ("I know that 5 and 3 makes 8.") and apply that understanding to help them solve subtraction problems ("So 8 - 5 must be 3.
