Tuesday, January 24, 2012

Multiplication Ain't No Repeated Addition

Yesterday, I and several other teacher leaders from across the district, had PD and I learned something that shocked me.
Multiplication is NOT repeat addition.
Ok, I am no Master Mathematician.  In Common Core language, I lack a mathematical mind.  (I mean it, I have never had this.)
So I have always taught math trying to avoid teaching formulas or having only one method. 
(Teaching the topic in multiple perspectives is an idea from my dad, did I mention he teaches Accounting at a university.)
Well, back on topic.  The 5th grade teachers were talking about a new term they were going to be teaching the kids, scaling. 
What is scaling you ask?
Well I Googled it, and this is what I found: Multiplication Ain't No Repeated Addition
The long and short of it.  I sat there thinking "I HAVE SCREWED MY STUDENTS UP... FOREVER!"
Of course, I know that's not true.
Apparently, multiplying whole numbers this strategy works well.  When it comes to multiplying fractions with other fractions, this does not work as a strategy. 
As a third grade teacher, how have I fixed my mistake?  I explained to my students that we are going to have repeated addition as a strategy, but when they get past 3rd grade, this strategy will NOT be an option, because the numbers will either be too large or too small for this to be a good use of our skills.

Please tell me I was not the only one who has taught it this way?


  1. Many of my students used repeated addition (and still do) when they were asked to solve multiplication problems. In my opinion this is a wonderful stepping stone-but then again I am new to teaching 3rd grade math this year. I can see how it would not be the best strategy with large numbers, but I would hope by the time the students get to that they would have memorized the basic facts . . . hopefully :)

  2. Just found your blog and followed! Interesting post! Sure makes you think! Can't wait to read more of your blog!

    Peace, Love and First Grade

  3. I think repeated addition is a good way to introduce multiplcation to young students. Telling them that this will become difficult as the numbers get bigger should be addressed to them. That way it's no surprise when they can't do repeated addition to a problem like 12x22.