This Fluency Activity is a part of the Lesson 4, Unit 2, Grade 4. This fluency activity deepens student understanding of the composition and decomposition of unit conversions, laying a foundation for adding and subtracting liters and milliliters. The numbers in bold type indicate the point at which the direction of the counting changes. Direct students to count by liters in the following sequence: 500 mL, 1,000 mL, 1,500 mL, 2,000 mL, 2,500 mL, etc.