## Lesson: Inverse Relationship Between Addition and Subtraction

Developing the Concept

Once children are proficient in finding related facts, they are ready to discover fact families.

**Materials:** per child: 10 red cubes and 10 blue cubes

**Preparation:** none

**Prerequisite Skills and Concepts:** Children should understand addition and subtraction. They should also understand sums through 12 and subtracting from 12 or less, the numbers they are working on. They should also understand related facts.

Remind children about the related facts that you covered. Take time to review several pairs of related addition and subtraction facts.

**Wrap-Up and Assessment Hints**

Children need lots of practice with related facts. As you assess, give one fact and have the children write the fact family. Or ask questions such as, Can you write a related addition fact for 12 − 5 = 7? As you observe, check to see that children are using the correct sign and are doing the correct operation for the sign that is in the exercise.