What is a Number Family for 3?

S0-SA1-1215

Grade Level:

Pre-School – Class 2

All domains without exception

Definition

What is it?

A Number Family for 3 is a group of addition and subtraction facts that use the same three numbers. For the number 3, these facts show how different parts come together to make 3, or how 3 can be broken apart.

Simple Example

Quick Example

Imagine you have 3 ladoos. You can have 1 ladoo and your friend has 2 ladoos, making 3 in total (1 + 2 = 3). Or, if you have 3 ladoos and eat 1, you are left with 2 (3 - 1 = 2). This set of facts using 1, 2, and 3 is a number family for 3.

Worked Example

Step-by-Step

Let's find the number family for 3 using the numbers 1, 2, and 3.

Step 1: Think of two numbers that add up to 3. We can use 1 and 2.

Step 2: Write the first addition fact: 1 + 2 = 3.

Step 3: Reverse the order of the numbers being added to get the second addition fact: 2 + 1 = 3.

Step 4: Now, use subtraction. Start with the total (3) and subtract one of the parts (1): 3 - 1 = 2.

Step 5: For the last fact, start with the total (3) and subtract the other part (2): 3 - 2 = 1.

So, the number family for 3 (using 1, 2, 3) is: 1 + 2 = 3, 2 + 1 = 3, 3 - 1 = 2, and 3 - 2 = 1.

Why It Matters

Understanding number families helps you solve math problems faster and build a strong foundation for mental math. This skill is crucial in careers like banking, where you quickly calculate transactions, or in business, where you need to manage budgets and inventory efficiently.

Common Mistakes

MISTAKE: Only writing addition facts and forgetting subtraction facts. | CORRECTION: Remember that a number family includes both addition and subtraction facts using the same three numbers.

MISTAKE: Using numbers that don't belong in the family (e.g., trying to use 4 for a number family of 3). | CORRECTION: Ensure all facts in the family use only the three specific numbers involved.

MISTAKE: Mixing up the total with the parts in subtraction (e.g., writing 1 - 3 = 2). | CORRECTION: In subtraction facts, always start with the largest number (the total) and subtract one of the smaller parts.

Practice Questions

Try It Yourself

QUESTION: Which of these is NOT part of the number family for 3 using 0, 3, and 3? (a) 0 + 3 = 3 (b) 3 + 0 = 3 (c) 3 - 0 = 3 (d) 3 - 3 = 0 (e) 3 + 3 = 6 | ANSWER: (e)

QUESTION: Write all the facts in the number family for 3 using the numbers 0, 3, and 3. | ANSWER: 0 + 3 = 3, 3 + 0 = 3, 3 - 0 = 3, 3 - 3 = 0

QUESTION: If the number family for 5 uses the numbers 2, 3, and 5, write all four facts. | ANSWER: 2 + 3 = 5, 3 + 2 = 5, 5 - 2 = 3, 5 - 3 = 2

MCQ

Quick Quiz

Which set of facts correctly shows a number family for 3 using the numbers 1, 2, and 3?

1 + 2 = 3, 2 + 1 = 3, 3 - 1 = 2, 3 - 2 = 1

1 + 3 = 4, 3 + 1 = 4, 4 - 1 = 3, 4 - 3 = 1

1 + 2 = 3, 3 - 1 = 2, 3 + 0 = 3

1 + 2 = 3, 2 + 1 = 3, 3 + 1 = 4, 3 - 2 = 1

The Correct Answer Is:

Option A correctly lists all four addition and subtraction facts using only the numbers 1, 2, and 3. The other options include incorrect facts or numbers that are not part of this specific number family.

Real World Connection

In the Real World

When you pay for something at a local kirana store, say a chocolate for ₹10 and a biscuit for ₹5, the shopkeeper might quickly calculate the total as ₹15. If you give ₹20, they know to return ₹5. This quick mental math is based on understanding number families (10 + 5 = 15, 15 - 10 = 5, 15 - 5 = 10).

Key Vocabulary

Key Terms

ADDITION: Putting numbers together to find a total | SUBTRACTION: Taking one number away from another to find the difference | FACT FAMILY: A group of related addition and subtraction facts using the same three numbers | TOTAL: The result of adding numbers together

What's Next

What to Learn Next

Great job learning about number families! Next, you can explore number families for bigger numbers like 5 or 10. This will help you become even faster and more confident with your basic addition and subtraction skills.