Like other experienced teachers, I've taught the same concepts and skills to students so many times that I've developed a huge repertoire of activities that I can build into my instructional time. I have activities that provide more scaffolding if the kids didn't really seem to understand the lesson, and activities that will extend student learning if what I taught was too easy. I have activities that will take a long time if my lesson ends early, and activities that can be done quickly if my lesson takes too long.
The flexibility and text book quality of the math worksheets, makes Math-Aids.Com a very unique resource for people wanting to create and use math worksheets. The answer key is included with the math worksheets as it is created. Each math topic has several different types of math worksheets to cover various types of problems you may choose to work on.