When students finish their math tests and want to hand them in, I always ask, "Did you check your work?" Often the answer is "yes," but if it's not, I won't take the paper until the student does check over their work. How do they do this checking? Do you know what I'm going to say?
Here's what they do - they look at the questions, basically make sure that all the questions were answered, and again try to hand the test in. Unless they are clearly taught otherwise, many students seem to understand "checking your work" to mean "checking to see if everything is done." What does checking mean to you?
What does it mean to me? How do I think students should check work?
I teach them to use the following strategies. They aren't always thrilled by the extra time and effort this real checking takes, but they do find that it helps.
1) Redo every problem, on a separate piece of paper, without looking at the work that was already done (when they look at the work they already did, it influences them and they sometimes make the same mistake again). Then compare the original work and answer with the redo.
2) Use the opposite operation to check, if possible. If the problem was an addition problem, subtract one of the addends from the sum. If it was a division problem, use multiplication to check. You know what I mean:-)
3) Ask whether the answer is logical. If the problem was 2.56 x 7.91, an answer of 2.02496 (instead of 20.2496), is not logical.
4) Substitute the solution into the equation, if possible. If the solution is correct, the equation will be true.
5) If the test includes word problems, reread each problem carefully to be sure all of the information was understood correctly. Look for numbers that are written as words rather than digits.
Be sure the answer actually answers the question the problem is asking.
I made a How to Check Your Work reminder sheet for students to keep in their notebooks. You can download it if you'd like - there's a colored version and a black and white version, in case you want to print on colored paper. I hope you can use it!