This Fluency Activity is a part of the Lesson 15, Unit 5, Grade 4. This fluency activity reviews skills applied in Lesson 14. Fluency drills are fun, fast-paced math games. Be careful not to leave English language learners behind. Make sure to clarify that common unit, common denominator, like unit, and like denominator are terms that refer to the same thing and are often used in math class interchangeably.