This Problem Set is a part of the Lesson 3, Unit 4, Grade 2. In this lesson, students use relationships between the numbers to develop a variety of simplifying strategies to add and subtract multiples of 10, with adding the complexity of some ones, so that the ones digit is close to a multiple of 10. Students will use arrow notation to show their reasoning. For example, 48 + 19 is one less than 48 + 20, therefore 48 + 19 = 48 + 20 -1 = 68 -1 = 67.
