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Peanut Buttering (Reducing) Fractions

Today for fun, we repeated an activity Bruce and I had done a while ago, called Peanut Buttering fractions.  This is a lesson on reducing fractions that I learned with I was going through teacher training for Constructivist math.  It is a wonderful example of a hands-on activity helping children construct their own understanding of a mathematical concept.  The whole word “reducing” doesn’t make a lot of sense when you think about it, because the actual quantity of the fraction your reduce never decreases or diminishes.  Peanut buttering, makes a lot more sense.

To start, I asked Bruce to tell me which fraction of the MnMs were red.  He answered 3/9. 

By this point, Bruce totally remembered what to do next, which was the reduce the fraction with peanut butter.  But with a child new to the activity, there is a lot language prompting you can introduce to help guide them to discovering how this works on their own.  “Look for groups.  Do you see a way to group the candy evenly?  Instead of having so many red candy, can you make a clump with peanut butter?  Oh, you make a red clump of three, can you make green clumps of three?”  etc.

After peanut buttering, 3/9 of the candy being red, becomes 1/3 of the candy. 

Here’s another problem we did.  By this time, things were getting pretty sticky!

What fraction of the candy is green?  10/20

Bruce’s first attempt at peanut buttering, and he turned 10/20 into 2/4.

I asked him to if he could peanut butter even more, and he made 2/4 into 1/2.  1/2 of the MnMs were green.

On a side note, my MIL brought that giant tub of Jif over to our house when my husband and I were in Europe.  We usually eat organic peanut butter instead.  The hydrogenated stuff actually works better for this activity though, because natural peanut butter is a bit too slippery.


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