Have your kids mastered the multiplication tables? Mine struggled initially despite making effort. I tried to help them by making silly rules for the most difficult numbers. In retrospect I think it worked because I helped them by creating visual images that they could recall.
For example, 7 x 8 = 56 is difficult for me and other, but by reorganize the numbers involved, you get 5-6-7-8. If they recalled this, it was easier to remember.
For the 8 x 9 = 72 it was more difficult to find something to associate with, so we simply called it the wizard. And wizards are usually old. Actually 72 years of age. And with that image in their head, they remembered it.
This methods leaves something to wish for, especially to us non-educator parents. Instead, there is a visual method for learning multiplication that you can teach your kids. Educator Sarah Major at Child1st has written about the right brained way to teach kids to count.
Study-skills-for-all-ages.com has multiplication work sheets that you can print and apply the method to.