I love the idea of a pre-check. Thanks for the suggestion.
We too have found that "easy" questions = sloppy work.
DD10 is such a perfectionist that I actually welcome the mistakes. I never make a big deal about her making mistakes. They tend to happen when she isn't paying attention and she knows it.
With DD8, I find that she just doesn't see things sometimes -- skips a critical word or an entire question. She rushes through thinking that she knows what she is doing or what the question is. I can ask her to look at it again and she still seems to miss the same info. For her, I have to go back and break things down into more manageable pieces. I used to literally block off the rest of the page so that she could focus on one paragraph/question. Now she can do this without the visual aid. Sometimes it helps to have her read the question out loud and then she'll catch her mistake.