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Decimal Operation Help!



We've been spending a bit of time on decimal operations. I have five math classes, and in four of the five, our work with decimal operations has gone pretty well. There are a few students who are still mixing up their rules - when to line the decimal point up and when not to. When to count the digits behind the decimal points and when not to. However, in the fifth math class, there are many students who are not "getting it," even though did work with decimal operations last year. Part of the not getting it, I believe, is due to the fact that they don't actually look at their answers and think about whether or not they make sense. For example, many students will take a problem like 18.9 - 8 and get 18.1 as the answer....and they don't notice that it doesn't make sense to take 8 from 18 and still have 18 left. We've had discussions, gone through so many examples, and they've practiced the operations individually (and did very well when adding and subtracting were the only operations we were practicing). But when we put adding, subtracting, and multiplying together, forget it! Everything flies out the window! (We haven't done division yet, but I find that this doesn't normally mess them up like adding/multiplying confusion does).
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Since I feel at somewhat of a loss, I made a new notes sheet for the to use as a reference. They already have a fold it up in their Fold It Ups books, but it seems that they don't use it (or don't understand it?) So, this new one is more "visual." It looks a bit busy to start with, but I'm hoping that the arrows and different shapes will help to trigger something in their memories when they try to remember certain rules (until their number sense gets a bit stronger).

We'll see if this helps!

Anyone have any special ways to help struggling students to keep these operations straight?









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