This Fluency Activity is a part of the Lesson 13, Unit 6, Grade 2. During Topic C and for the remainder of the year, each day's fluency activities include an opportunity for review and mastery of the sums and differences with totals through 20 by means of the Core Fluency Practice Sets or Sprints. Practice Sets, along with details about the process, are provided in Lesson 12. The next page(s) include student-facing material for this activity. Name Date 1. 10 + 2 = 21.