RRoomTeach

Posted on 11/01/09

I use several different methods of teaching addition and
subtraction of positive and negative numbers in my resource
room. The first thing I do is teach adding positive and
negative using red/black chips - red for negative and black
for positive - we lay out whatever amount is being added - we
look for "Zero pairs" - (one positive and one negative chip
form a zero pair which cancel out) and then we see what is
left in front of us.

When we do subtracting integers I DO NOT teach them the KCC
or Add the Opposite algorithm initially. They will never
understand the concept behind subtracting integers if they
always automatically turn them into addition problems. We do
the same process with chips, however we add zeros pairs if we
cannot complete the problem. For example -6 - +4. We lay out
6 red chips (negatives). When we see that we cannot take away
4 positives (blacks) because there are no blacks we talk
about adding zero pairs. From the addition portion of the
lesson we have already learned that a zero pair has no value -
its zero, so theoretically we can add as many zeros as we
want to any amount and never change the value. So in this
example we would add 4 zero pairs (which means putting 4 red
and 4 black chips down on our mat). We should now have a
total of 10 red and 4 black chips in front of us (the
original 6 red, the 4 zero pair reds and the 4 zero pair
blacks). Now we can subtract +4. We remove the 4 positive
chips (blacks) and see what is remaining. 10 red. or -10. So -
6 - +4 = -10. Whew. That was a lot of typing - does this
process make sense?

Hope this helps

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