Like Topic A with the study of factors, Topic B extends the study into division. In Lessons 4 and 5 students will relate the meaning of the unknown in division to the size of the groups and the number of the groups. They will learn the vocabulary of quotient. Then in Lesson 6 students explore division in the context of the array model, interpreting arrays by writing division sentences. They use arrays to write multiplication sentences and find unknown factors, then write division sentences where the quotient represent the same as the unknown factor. By the end of the topic students use the vocabulary of quotient and factor as the discussion moves toward solidifying understanding of the relationship between multiplication and division.