Divide and Conquer


I like to find different ways for students to understand the invert and multiply algorithm and this summer I have seen some good ideas for representing division of fractions.

First I will direct you to Graham Fletcher’s blog, GFletchy. Earlier this year he wrote about his method which I like for daily use in the classroom. His strategy is to have students find ways to turn the denominator into one whole.  In his post he also directs you to two other sources for this topic. One source is Fawn Nguyen who wrote about a rectangular model, an interesting model for conceptual understanding. The other source is Christopher Daniel’s blog, Overthinking My Teaching. He discusses a model I had never heard of before, using common numerators to divide fractions.

I also want to share an online widget that I found years ago called the DIM Calculator. This widget allows students to enter any two fractions then follow the instructions to learn why invert and multiply works.

I have used the DIM Calculator in the past, but I will definitely be introducing these other ideas to my students in the future.

Posted by Ilana Cyna

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