Chapter 4 of Making Number Talks Matter is about subtraction. The authors suggest beginning with subtraction because students in the upper grades may see addition problems as “too easy.” As we all know too well, subtraction is a challenge for many of our students. Exposure to a variety of strategies may help students feel more flexible with subtraction problems.
In addition, the authors stress the importance of students understanding that the meaning of subtraction includes both subtraction as the removal of something and as the distance between two numbers on the number line. Because students generally think of subtraction as “take away,” the authors focused the number talk strategies in this chapter on subtraction as the distance between two numbers.
The picture below is a quick overview of how students may articulate how they use each of the strategies, as titled in the text. I chose to use a different problem than the one in the book so that I could apply my own explanations to each strategy.
While I have seen students use the “Add Instead” and “Decompose the Subtrahend” strategies, the other three strategies seem more difficult for students to use because of the thinking necessary to understand them. However, exposure to and the rehearsal of these skills will produce students with strong strategic thinking and computational skills.
In the latter part of the chapter, the authors give a detailed explanation of how to develop the strategies above. This section includes a more in-depth description of the strategy, sample problems, and questions to probe when students use each strategy. At the end of the chapter, the authors illustrate how the strategies apply to fractions, decimals, and integers.
Reference: Humphreys, C and Parker, R. (2016). Making Number Talks Matter. Portland, Maine: Stenhouse Publishers