What is a Fact Family for 9?

S0-SA1-1310

Grade Level:

Pre-School – Class 2

All domains without exception

Definition

What is it?

A fact family for 9 is a group of four related math facts (two addition and two subtraction) that use the same three numbers. For the number 9, these facts show how different numbers can add up to 9 or how 9 can be broken down.

Simple Example

Quick Example

Imagine you have 9 laddoos. If your friend gives you 2 more laddoos, you now have 11. But a fact family for 9 uses three numbers that always sum to 9. For example, the numbers 7, 2, and 9 form a fact family because 7 + 2 = 9, 2 + 7 = 9, 9 - 7 = 2, and 9 - 2 = 7.

Worked Example

Step-by-Step

Let's find the fact family for 9 using the numbers 5 and 4.

Step 1: Identify the three numbers. We have 5, 4, and 9 (since 5 + 4 = 9).
---Step 2: Write the first addition fact. Start with the two smaller numbers. 5 + 4 = 9.
---Step 3: Write the second addition fact. Flip the order of the two smaller numbers. 4 + 5 = 9.
---Step 4: Write the first subtraction fact. Start with the largest number (9) and subtract one of the smaller numbers (5). 9 - 5 = 4.
---Step 5: Write the second subtraction fact. Start with the largest number (9) and subtract the other smaller number (4). 9 - 4 = 5.

Answer: The fact family for 9 using 5 and 4 is: 5 + 4 = 9, 4 + 5 = 9, 9 - 5 = 4, and 9 - 4 = 5.

Why It Matters

Understanding fact families helps you see the relationship between addition and subtraction, which is super useful for mental math and solving problems faster. It's a foundational skill for careers like accounting, engineering, or even managing a small business where quick calculations are key.

Common Mistakes

MISTAKE: Using numbers that don't add up to 9 for the addition facts. For example, saying 3 + 5 = 9. | CORRECTION: Always ensure the two smaller numbers in your fact family actually sum up to 9.

MISTAKE: Forgetting to include both subtraction facts. For example, only writing 9 - 3 = 6 and missing 9 - 6 = 3. | CORRECTION: Remember that a complete fact family has two addition and two subtraction facts.

MISTAKE: Confusing the order in subtraction, like writing 3 - 9 = 6. | CORRECTION: In subtraction facts for a fact family, always start with the largest number (9 in this case) and subtract one of the smaller numbers.

Practice Questions

Try It Yourself

QUESTION: Write the fact family for 9 using the numbers 6 and 3. | ANSWER: 6 + 3 = 9, 3 + 6 = 9, 9 - 6 = 3, 9 - 3 = 6

QUESTION: If you know 9 - 1 = 8, what are the other three facts in this fact family? | ANSWER: 1 + 8 = 9, 8 + 1 = 9, 9 - 8 = 1

QUESTION: A vegetable seller has 9 tomatoes. He sells some, and 4 are left. What numbers form a fact family here, and what are all the facts? | ANSWER: The numbers are 9, 4, and 5 (since 9 - 4 = 5). The facts are: 5 + 4 = 9, 4 + 5 = 9, 9 - 5 = 4, 9 - 4 = 5

MCQ

Quick Quiz

Which set of facts correctly forms a fact family for 9?

2 + 7 = 9, 7 + 2 = 9, 9 - 2 = 7, 9 - 7 = 2

3 + 6 = 9, 6 + 3 = 9, 9 - 3 = 6, 6 - 3 = 3

1 + 8 = 9, 8 + 1 = 9, 9 - 1 = 8, 8 - 1 = 7

4 + 5 = 9, 5 + 4 = 9, 9 - 4 = 5, 5 - 4 = 1

The Correct Answer Is:

Option A correctly shows two addition facts (2+7=9, 7+2=9) and two related subtraction facts (9-2=7, 9-7=2) using only the numbers 2, 7, and 9. Other options have incorrect subtraction facts or use different numbers.

Real World Connection

In the Real World

When you're sharing a packet of 9 biscuits with friends, understanding fact families helps you quickly figure out how many each person gets or how many are left. For example, if you eat 3, you instantly know 6 are left because 3 + 6 = 9.

Key Vocabulary

Key Terms

FACT: A true statement or piece of information | FAMILY: A group of related things | ADDITION: Combining numbers to find a total | SUBTRACTION: Taking one number away from another | RELATIONSHIP: How two or more things are connected

What's Next

What to Learn Next

Great job learning about fact families for 9! Next, you can explore fact families for other numbers like 10 or 12. This will strengthen your number sense and make more complex math problems much easier to solve later on.