# Math Problem Solving Part 2: Separate (aka Some, Some Went Away)

In the previous post, I addressed problems dealing with an additive process (join; aka SSM).  In this post, I will show you some models to use for these types of problems:  Separate; aka Some, Some Went Away — SSWA.  I will share some models which are great for KG stories as well as templates that are helpful for intermediate students to use, especially when dealing with missing addend types.

As I previously mentioned, it is my belief that students should focus more on the verb / action in the story and not so much with the key words we often tell kids to pay attention to. Brainstorm actions that signify a subtractive process.  Post it in the class.  Keep adding to it as more actions are discovered. With this subtractive action, kids should quickly realize that there should be less than we started with when we take something away. Here is a FREE poster showing some of the most common subtraction action verbs. Click HERE to get your copy.

Some of the work mats pictures below come from the following source. These are great for KG-2nd subtraction storytelling.   Subtraction Pack: A Pinch of Kinder by Yukari Naka

Like with all story problems, I model how I reread the problem several times.

• Second read –Identify who and what the story is about (the action).
• Third read — Decide what to do with the numbers. Is a given number the wholetotal amount or part of the amount? Do I know how the story started? How it changed? The result?

Here are 3 types of subtraction story structures:

• c – a =  ____:  The result is unknown
• c – ___ = b:  How the story changed is unknown (aka missing addend)
• ____ – a = b:  The start is unknown.

With KG-2nd grade students, my advice is to focus on the concrete manipulatives and some type of mat to organize the pieces.  Ten frames and two-color counters are great to use. . . . Tell the story while the pieces are being put on the mat. Ten frames also help children develop number sense and focus on number bonds.

Try using the whole, part, part mat.  Move the manipulatives as you tell the story.

Use a numberline with Unifix cubes.

With these examples, place the starting amount on the mat. Place the ones being subtracted in the cup.

For intermediate students, utilize a template so they consistently see the following:

• If I know both parts, add them together.
• If I know one part and the total, I can solve 2 ways:  add to or subtract  (More on adding to strategies using mental math and open number lines in the future.)

Questions help children think through the process:

• Is 48 all of the m&ms or part of the m&ms? (all)
• Is 32 all of the m&ms or part of the m&ms? (the part that was sold)

Questions help children think through the process:

• Is 48 all of the m&ms or part of the m&ms? (all)
• Is 16 all of the m&ms or part of the m&ms? (the part that is left unsold)

Questions help children think through the process:

• Is 32 all of the m&ms or part of the m&ms? (the part that was sold)
• Is 16 all of the m&ms or part of the m&ms? (the part that was left over)

I’m glad you are here! Any comments or suggestions? Would love to hear from you!

Next time, I will focus on comparison problems.  These do NOT involve additive or subtractive actions. So we will use a different visual model to represent them. Stay tuned!!