Lesson objective: Multiply decimal numbers less than one using concrete models or drawings and strategies based on place value; relate the strategy to a written method and explain the reasoning used.

This lesson helps to build procedural skill with decimal multiplication with factors less than one. An array is used here because it supports the importance of place value. This work develops students' understanding that the relationship between factors and products remains the same with decimal numbers.

Students engage in Mathematical Practice 7 (Look for and make use of structure) as they make the connection between the size of factors and products and learn to multiply and then divide by powers of ten using the compensation method.

**Key vocabulary:**

- area model
- array
- compensate
- factor
- product
- reasonable
- relationship

**Special materials needed:**

- flats, rods, and cubes
- number lines
- squared paper