Common Core math question is Algebra!!!! *gasp*
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@xaade Of course, it helps more once you're working with larger numbers.
For example, 39 + 39? Well, that's almost the much easier 40 + 40, except you added one to each number (before doing the main addition) and you've got to take that off again at the end.
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@dkf The distributive law can simplify multiplications, too, as in
5 * (34 + 6) = 5 * 40implies5 * 34 = 5 * 40 - 5 * 6 = 170.
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@dkf said in Common Core math question is Algebra!!!! *gasp*:
@xaade Of course, it helps more once you're working with larger numbers.
For example, 39 + 39? Well, that's almost the much easier 40 + 40, except you added one to each number (before doing the main addition) and you've got to take that off again at the end.
The problem is that if you're teaching addition, and you show this method, you've snuck subtraction and algebra in there.
IOW, your simpler method of addition requires more knowledge than just addition.
And then it becomes turtles the whole way down.
It's great to teach once the kids have a grasp of the standard way of doing addition and subtraction. Not as the first method introduced of doing addition.
