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Saturday, October 31, 2009

What's the Difference?

Well, we gave a subtraction test this past Thursday, and MOST of my kids did pretty well. Which is a good thing, since we've been practicing subtraction pretty extensively for the past 2 weeks!!

The good news is that I started the year with about 4/5 of my kids thinking that 2-8=6 (not regrouping), and now I only have 4 or 5 kids that still do that on a regular basis. In fact, one of the questions on the test was "How do you know when you are supposed to regroup on a subtraction question?" I am pleased to say that all but about 3 of the kids answered something to the effect of "When you have a tiny top and a big bottom."

Of course, some of my kids who still don't regroup got that question correct, so they KNOW when they are supposed to regroup in theory, they just don't put it into practice...

What disappointed me was the other short answer question. Much like on our addition test, where I was looking for the word 'SUM,' I posed a similar question on this test:

What is the math word that means "the answer to a subtraction problem?"

The answer, of course, is "Difference." This is something that we have talked about repeatedly, used in word problems, and it was even up on the board on a Clue Word list. However, I only had 16 kids (out of 40) that got this question correct.

Wrong answers included the following:

Sum (I guess they missed it on the last test and hoped to jump on the bandwagon this time)

Check your work (Good advice, but does not answer the question)

How many more

Take away


Left (These words at least are subtraction clue words, but still don't answer my question)

Subtract (Too obvious, kid)

And my personal favorite (*SARCASM ALERT!!*):


Yeah, the answer to a SUBTRACTION problem is called "The Addition."

Just when I thought we had mastered the concept of opposites...


loonyhiker said...

This brought back memories of when my mother used to make me check all my subtraction problems by making me add up to see if I got the same top number. I would actually have to rewrite the problem as an addition problem beside the subtraction problem. I hated doing that but I guess it helped because I was very good with math and got good grades.

Mister Teacher said...

Loony, that is an excellent way to check your answers, and I insist that my kids do it as well! Of course, on the test, some kids did NOT get the same top number but went on anyway, or even worse, they erased and changed their addition answer to make it LOOK like it matched the original number! Which made it look like they had added 3+3 and gotten 2 or something foolish like that.