Are the problems too close together? Make sure you can distinguish between the problem number and the actual problems. The problem numbers should be less obtrusive. Students with and without ADD and ADHD can become distracted by too many distractions!?
Some free math worksheet sites allow you to choose criteria, click a button, and generate a web page of problems. These types of web sites allow for worksheets that produce random digits in numbers. You should find more robust problems sets on web_generated math worksheets. How can web sites give away math worksheets? Do free math worksheet web sites make money? Yes and no. Let's just say it is very important that you visit and support your favorite free math worksheets web site!