If you do want to produce your own worksheets and don't have the Microsoft software, you can download free tools like OpenOffice or use an online word processor or spreadsheet such as the free Google Docs which help you do similar tasks. You just need to create a table with as many rows and columns as you need and then type in some numbers before printing it off for your children to practice _ depending on the level of complexity choose single digits or multiple digits. If you're not sure what level to start at, aim low, start with easy numbers and see how your child goes, the self_esteem boost they'll get from acing the first worksheet will give them confidence for more difficult math problems.
Maths Based Worksheets _ Children can work with simple numbers worksheets from quite an early age and you will have greater success in getting them to work on the worksheets if you combine that learning work with something practical, or at least something they enjoy doing. For example, if you are using a simple addition and subtraction worksheet with your child, draw or type up another sheet of with squares and numbers printed onto them. Instead of writing the answers to the questions on the worksheet you can get your child to cut and paste the required numbers for the answers from from the second worksheet onto the first.