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!