5 Subtraction Algorithms: Great to do in Guided Math Groups

Posted on August 31, 2011. Filed under: Assessment, Common Core, During the Guided Math Lesson, Elementary math, Guided math | Tags: , , , , , , , , |

We are continuing our discussion about the need to teach our students a variety of strategies and algorithms.  Remember that two of the Common Core Standards that discuss algorithms are

  • 3.NBT.2. Fluently add and subtract within 1000 using strategies and algorithms based on place value, properties of operations, and/or the relationship between addition and subtraction.

4.NBT.4. Fluently add and subtract multi-digit whole numbers using the standard algorithm.

Here are some great resources for Subtraction Algorithms:

1) Use the Number Splitting Strategy for Subtraction

Resource 1

Resource 2 

Resource 3 : How does this scaffolded organizer teach and shape thinking?

Resource 4 :  The common core wants students to be able to discuss whether problems are mathematically true or false beginning at first grade

2) Open Number line Strategy for Subtraction (See this blog for several resources)

Resource 1

Resource 2 

3) Subtraction Using the Counting Up Strategy

4) Compensation Strategy for Subtraction

5) Traditional Trade First Algorithm for Subtraction  

Resource 1 (As you watch this video, think about how the graphic organizer scaffolds students thinking about the traditional algorithm).

Resource 2 (What can we tell about Mattie’s sense of place value by the way she discusses the problem?)

Resource 3  (Watch this video and then think about what strategies the teacher uses to get across the concept.  Is she building conceptual understanding?  What purpose does the poem serve?  Does the poem help to build conceptual understanding or is it just a great mnemonic device?)

So, what do you think of these strategies and algorithms?  How many of them do you use?  Which ones would you introduce first and why?  You should definitely discuss these in small guided math groups so that students get to discuss what they are doing and listen to others.  This ties right into the mathematical practices that state that students should be talking and listening to each other discuss math.

Happy Mathing,

Dr. Nicki

P.S. Be sure to read the other posts on algorithms.  We will be discussing all four basic operations during this series.

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