Relating addition and subtraction means understanding how the two operations are connected. Addition puts numbers together to make a total, while subtraction takes away or finds the difference. They are inverse operations, which means they undo each other.
If you can check an addition problem by using subtraction, or check a subtraction problem by using addition, then the sentences are related.
To identify related addition and subtraction sentences, look for the same three numbers being used. One sentence will show how the parts make the whole (addition), and the other will show how the whole can be broken into parts (subtraction).
Every related set of numbers can form two addition sentences and two subtraction sentences.
A fact family is a group of related addition and subtraction sentences that use the same three numbers. Fact families show how addition and subtraction are connected.
Fact families always balance addition and subtraction sentences. They help you see that numbers can be used in more than one way.
You can use related addition and subtraction sentences to check if your answer is correct. Solving the “inverse” problem should bring you back to the original number.
This strategy is useful for multi-digit problems where regrouping is needed. It helps confirm accuracy and builds confidence in your answers.