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Q&A #221


Teaching dividing fractions

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From: Rick (for Teacher2Teacher Service)
Date: Apr 20, 1998 at 04:05:08
Subject: Re: Teaching dividing fractions

One thing you might try is to have them "play around" with some divisions
until they come up with an algorithm, or at least until they start thinking 
about it a bit. Ask them to draw 3 squares, divide each into 4 parts, and ask 
them how many 3/4 there are there. You hope that they would shade in 3 out of 
4 of the small squares in each box and see that there is another "3/4" by 
taking the one left over from each of the boxes. They therefore have four "3/
4"s and therefore 3 / 3/4 = 4.

Ask them now to do 3 / 1/4 (12). Have them play around with some other
combinations that come out to be whole numbers and ask them to now look at the
numbers and decide how they could use the numbers to get the correct results.
They may not come up with the algorithm that you mentioned (aka invert and
multiply), but at least they have thought about what is going on.

Then, talk about the "flip and multiply" as an algorithm that someone thought
about that converts the thing you are dividing into a fraction with a "bottom"
(denominator) of 1.

Hope this helps some...maybe someone else will have some suggestions as well.

Good luck,

Rick

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