Lesson 14 starts off Topic E introducing students to multiplication by 4 through skip-counting objects in array models. Students revisit the commutative property in Lesson 15, this time modeling commutativity using both arrays and tape diagrams. For example, students might initially draw a 2 by 4 array and a 4 by 2 array. Then they see 2 bars of equal length; one with 4 equal parts and the other with 2 equal parts. Now they have arrays that show (2 x 4) = (4 x 2), as well as tape diagrams that reflect the equality. In Lesson 16 students examine the distributive property in greater depth. This lesson introduces the 5 + n pattern as a strategy for finding unknown facts involving 4. For example, students know that 4 x 5 is 20, so 4 x 6 is the same as 20 + 4 more, which totals 24. By Lesson 17 practice of multiplication and division facts is dedicated to modeling the relationship between operations using facts of 4.