This Problem Set is a part of the Lesson 12, Unit 3, Grade 3. In this lesson, students use the distributive property to establish the 9 = 10 - 1 pattern for multiplication. They learn to think of each nines fact as a well-known tens fact minus one unit. For example, 9 × 8 = (10 - 1) × 8 = (10 × 8) - (1 × 8) = 80 - 8 = 72.
