# Missing Factors

## Developing an Algorithm for Decimal Multiplication

For CMP2, Bits and Pieces III, Problem 2.2.

The CMP3 Decimal Ops Unit is substantially different than the corresponding Unit in CMP2. This roughly corresponds to Investigation 3 of Decimal Ops.

The focus of this video is on the progress made by students towards understanding and using an efficient algorithm for multiplying decimals. At the end of Problem 2.1 at least two different students have proposed algorithms, but it is not clear that everyone has understood why these work.

Real time is 1.5 class periods.

As you view the video, consider the following:

- What is the evidence of students’ understanding and reasoning? What prior understandings do you see students using or building upon?
- What is the evidence of students’ use of the Mathematical Practices from the Common Core State Standards for Mathematics (CCSSM)? To what extent are students growing in their sophistication of their use of the Mathematical Practices?
- Were there any “aha moments” in the video?
- How is the teacher facilitating the development of students’ understanding and reasoning?
- As a teacher, how would you use the information from this lesson to plan the next lesson?