These are charts I created to help my students with those tricky Addition and Subtraction Facts. What we would do is first write in the answers to each fact that we know right away (the easy ones). Then we would highlight the facts that we don't know right away (the hard ones). Then, we would fill in the answers to the hard ones by looking for patterns. It's really easy for them to see patterns using this kind of chart. Looking for patterns helps in understanding number sense instead of just memorizing the facts.
Patterns in Addition and Subtraction Facts
This is a very low complexity level for students. This would benefit students in either first or second grade. These should be basic mathematical facts for students in grade 3.