Teacher2Teacher Q&A #16511

Modeling Subtraction of Integers using Red and Yellow Counters

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From: Jeanne (for Teacher2Teacher Service)
Date: Jan 14, 2006 at 23:48:53
Subject: Re: Modeling Subtraction of Integers using Red and Yellow Counters

Hi Mimi, I use a manipulative called "tile spacers" to help me teach addition and subtraction of integers. They are shaped like plus signs and can be purchased from a home improvement store that sells ceramic tiles. To make negative signs just take a pair of scissors and snip two "legs" off. These have the advantage of looking like "+" and "-" signs. I am not saying that you should go out and purchase these items, but these manipulatives remove at least one level of interpretation and for some struggling students this makes a big difference. Before I discovered tiles spacers I used tiles to teach this concept and had my students write "+" on one side of the tiles and a "-" on the other. Anyway, I begin by showing my students that a "+" and a "-" make a zero and that "++" and "--" make zero and that "+++" and "---" make zero...etc. We start each problem with some zeros on their work space. I call them "zeros" and not "a plus and a minus." I take advantage of their understanding that adding zeros does not change the value of a situation. Example: 3 - -4 "3 minus -4" This means we put in 3 and we TAKE OUT -4 ------------- ------------- ------------- | +++++ | | +++++ +++ | | +++++ +++ | | ----- | --->| ----- | --->| - | ---> Value = 7 | | | | | | ------------- ------------- ------------- Value = 0 Put in 3 Take out -4 Hope this helps! -Jeanne, for the T2T service

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