This Fluency Activity is a part of the Lesson 15, Unit 4, Grade 1. This fluency activity reviews how to use the Level 3 strategy of making ten to add two single-digit numbers. Reviewing the make ten strategy prepares students for today's lesson, in which they systematically connect these problem types to analogous problems within 40 (e.g., students make ten to solve 9 + 5 and then apply the same strategy to solve 19 + 5 and 29 + 5). Repeat the activity from Lesson 14.