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subtraction
Posted:
Mar 21, 2001 6:15 PM
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Hi
I have a question. How do you teach subtraction? No, that's not
really my question. What I really want to know is how you feel about
the wording that students use to express subtraction.
As I grade "Mr. Pearson's Statistics Lesson" in the Middle School PoW,
I find that many students are correctly finding the range using
subtraction. However they are having a terrible time trying to tell me
what they are doing.
Some of the things I've seen are:
"i found the range which is the difference between the least and the
greatest numbers in a set. I subtracted 99 from 45 and got 54."
"The way I got the range of the test scores was by subtracting the
highest score which was 99 by the lowest score which was 45 and I got
54 as the range. 99-45=54"
"i took 99 witch was the highest socre and subtracted it by 45 witch
was the lowest socre, and i got 54."
"to find the range i must minus the hightest and lowest extremes.
99-45 = 54"
I don't recall ever learning to subtract "by" a number. Is that
terminology something I missed?
I'm not denying credit if they subtract "by," in fact I'm seeing it so
much that I hardly notice it any more. ;-) Is it something you get
used to, like not capitalizing the word "I"?
We really have to pick and choose our battles, right?
I am denying credit and asking for revisions if students tell me that
45-99 is 54. Please say it isn't so!
:-)
Judy
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