**Objective: **

Understand that place value and array models can make it easier for us to multiply two multi-digit numbers.

This optional activity can be used instead of or in support of Unit 2 Lesson 3.

**Math concept addressed:**

In this Guided Collaborative Task, students will use their knowledge and understanding of place value to figure out how to multiply multi-digit numbers. Students will figure this out by using base ten blocks to model place value.

Under the “Additional materials” tab, you’ll find a place value mat that may be used as students model place value with multi-digit numbers.

**Prior knowledge needed: **

Students bring prior knowledge of multiplication arrays. This prior knowledge is extended to multi-digit arrays as students decompose both factors by place value in the array.

**How students will collaborate:**

Collaboration happens through a collaborative structure called "the interview". Students see a problem that they have an opinion about and then interview one another about their work.

**Mathematical practice featured:**

Students engage in Mathematical Practice 1 (Make sense of problems and persevere in solving them) as they apply the base ten array concept to help them determine what is the best way to complete the array with two sets of double-digit numbers.

**Key vocabulary:**

- array

- factor

- place value

- product

**Special materials needed:**

- base ten blocks (optional)