A fact family is a group of math facts that use the same numbers. For early learners, fact families show how addition and subtraction are connected. A Part-Part-Whole triangle helps students see that two smaller parts join to make one whole.
This makes number relationships easier to remember and use.
Key Facts
- A fact family uses the same three numbers in related equations.
- For the numbers 3, 5, and 8: 3 + 5 = 8.
- The turn-around addition fact is 5 + 3 = 8.
- The matching subtraction facts are 8 - 3 = 5 and 8 - 5 = 3.
- In a Part-Part-Whole triangle, the whole is the largest total and the parts are the addends.
- Addition puts parts together, while subtraction takes one part away from the whole.
Vocabulary
- Fact family
- A fact family is a set of addition and subtraction equations that use the same three numbers.
- Whole
- The whole is the total amount made when the parts are added together.
- Part
- A part is one of the smaller amounts that helps make the whole.
- Addition
- Addition is joining two or more numbers to find a total.
- Subtraction
- Subtraction is taking one number away from another to find what is left.
Common Mistakes to Avoid
- Putting the largest number as a part is wrong because the largest number is usually the whole in an addition and subtraction fact family.
- Writing only one addition fact is incomplete because a fact family usually has two addition facts with the parts switched.
- Starting subtraction with a part is wrong because subtraction facts in this family should begin with the whole.
- Using a new number in one equation is wrong because every fact in the family must use the same three numbers.
Practice Questions
- 1 Use the numbers 2, 6, and 8 to write the four facts in the fact family.
- 2 A Part-Part-Whole triangle has whole 10 and parts 4 and 6. Write two addition facts and two subtraction facts.
- 3 Explain why 3 + 5 = 8 and 8 - 5 = 3 belong in the same fact family.