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Topic: subtraction
Replies: 6   Last Post: Jul 22, 2001 8:49 AM

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Judy Ann Brown

Posts: 192
Registered: 12/3/04
Posted: Mar 21, 2001 6:15 PM
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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!


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