Remember to select worksheets that are the right level difficulty for your child. Get something too hard, and your child will become discouraged. Make it too easy, and they won't learn much.
Therefore creativity is a must for worksheets to be successful : Regardless if you are trying to review math, science, reading, writing, health, or social studies, your goal should always be to try and create something that will generate desire in the students to actually want to do it. If you can do this, the battle is practically over already.
Or you can usually find textbooks and workbooks at the public library, where you can also copy any worksheets that you want to use.
Solve vertical and horizontal computation problems