Reflection: Developing a Conceptual Understanding Multiplying 2-digit number by 1-digit number - Section 5: Closure


Using the expanded algorithm to multiply gives students a conceptual understanding.  Before Common Core, I did not like teaching the expanded algorithm because I did not use it in my personal life.  I always use the standard algorithm.  To be honest, I do not remember learning the expanded algorithm in school.  

As teachers, sometimes we like to teach what we are comfortable with doing ourselves.  After teaching the last two lessons on multiplying based on place value, I really like the expanded algorithm!  All of the students were able to grasp the concept of the distributive property.  A few of them still needs practice with the visual model, but they can break the problem into simpler problems, then add to get the product.

 I use to dread teaching multiplying a 2-digit by 2-digit.  A lot of the students could not follow the steps.  I'm hopeful that since they learned multiplying a 2-digit by 1-digit using the expanded algorithm, they will be successful on the 2-digit by 2-digit with the expanded algorithm and actually understand what it means.

  Using the Expanded Algorithm
  Developing a Conceptual Understanding: Using the Expanded Algorithm
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Multiplying 2-digit number by 1-digit number

Unit 12: Multiplying and Dividing
Lesson 9 of 23

Objective: SWBAT multiply a 2-digit number by a 1-digit number using strategies based on place value, then justify their answers using counters.

Big Idea: Students use counters to model the product of a 2-digit by a 1-digit multiplication problem.

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