Learning arithmetic facts involves applying strategies to problem-solving. In addition and subtraction, one of these is learning the twin facts, such as 3 + 3 and 4 + 4. Once your child has learned these, other facts can be derived from the twins. For example, 4 + 5 is intimately related to 4 + 4. If you know that 4 + 4 = 8, then 4 + 5 is just 1 more. Pose arithmetic facts to your child and ask her to solve them by deriving the answers from twins.