Sunday, October 5, 2014

Multi Digit Multiplication Strategies

Look at the problem below and think about how your students would respond to the two questions:
  • What is the value of the 2?
  • Why should we place a 0 in this space? 
photos of multiplication, anchor chart, mr elementary math, 3rd grade, 4th grade, 5th grade

If your students answer the questions by saying, "the 2 is worth 2," or "I placed the 0 in that area because I was always told to move it down," consider the idea that the student(s) do not fully understand the concept of multiplying multi digit numbers.

According to John Van De Walle, "For multiplication, the ability to break numbers apart in flexible ways is even more important than in addition or subtraction.  Your goal (as an educator) might be that each of your children has at least one or two methods that are reasonably efficient, mathematically correct, and useful with lots of different numbers."

In addition, the Standards of Mathematical Practice state that we should provide students opportunities to make choices and try out potential solution paths to answer problems.

When teaching, let's first question students to see how they solve a problem (student invented strategies).  If a limited number of strategies arise do not be afraid to introduce one of the strategies below.  These strategies develop deeper conceptual understanding while reinforcing the use of mental math.

photos of multiplication, anchor chart, mr elementary math, 3rd grade, 4th grade, 5th grade

 Another strategy that reinforces mental math and base ten understanding is partial products.
photos of multiplication, anchor chart, mr elementary math, 3rd grade, 4th grade, 5th grade

Click on the link below to see a Number Talks video in which students use various multiplication strategies:


For additional multiplication strategies, download the FREE multiplication strategies anchor chart by clicking on the picture below.



P.S. Let's revisit the answers to the two questions at the beginning of the post:
  • What is the value of the 2?  
    • Answer: The 2 is worth 2 tens or 20.
  • Why should we place a 0 in this space? 
    • Answer: We have a 0 in the second row because any multiple of ten or one hundred ends in a zero.  With our base 10 number system a zero serves as a place holder.    Using the example, 20 x 3 is 60 and 20 x 10 is 200.  Combining both 60 and 200 yields 260.  The 0 represents a place holder in the ones place and ultimately showing there are no ones in the 200 or 60.

9 comments:

  1. I teach fifth grade and this is in my plan book this week!!!

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    1. Hello Kelly. Thanks for your comment. I hope that these resources will help make your planning easier.

      Greg

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  2. Replies
    1. Thank you Tara. I always love your feedback.

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  3. I am a new follower! Love this visual of multiple strategies!
    Steph
    Simple Insights

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  4. I enjoy your blog. The only thing I would change about the anchor chart is calling one of the strategies the "House Method". So that students don't confuse this with just a trick or a process, I would put that as a visual for partial products. Just a thought.

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  5. Thank you! I will be sharing this with our 4th grade teachers this week.

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  6. Great ideas for teaching students different strategies for solving what can be a very difficult skill. Your blog gives me a wide range of ideas that really help me in my math class.

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  7. I am in high school and just started tutoring a 5th grader who does not understand the concept of carrying numbers in multi-digit multiplication. I think this is a nice way to help her understand without confusing her further. Thanks!

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