This Problem Set is a part of the Lesson 19, Unit 3, Grade 3. In this lesson, students use the place value chart to multiply by multiples of 10. To solve 2 × 40, for example, they begin by modeling 2 × 4 in the ones place. Then they relate this to multiplying 2 × 40 (or 2 × 4 tens), where the same basic fact is located in the tens column.