What is a Number Family of 3?

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Grade Level:

Pre-School – Class 2

All domains without exception

Definition

What is it?

A Number Family of 3 is a group of three numbers that are related by addition and subtraction. It shows how these three numbers work together to form different addition and subtraction facts. Think of it like a small family where everyone is connected!

Simple Example

Quick Example

Imagine you have 2 ladoos and your friend gives you 3 more. Now you have 5 ladoos. This forms a number family: 2, 3, and 5. You can also say 5 - 3 = 2 or 5 - 2 = 3.

Worked Example

Step-by-Step

Let's find the Number Family for 4, 2, and 6.
---Step 1: Identify the three numbers in the family. Here, they are 4, 2, and 6.
---Step 2: Find the addition facts. The two smaller numbers add up to the largest number. So, 4 + 2 = 6.
---Step 3: Write the 'turn-around' addition fact. You can swap the order of the smaller numbers and still get the same total. So, 2 + 4 = 6.
---Step 4: Find the subtraction facts. Start with the largest number and subtract one of the smaller numbers. So, 6 - 4 = 2.
---Step 5: Write the other subtraction fact. Again, start with the largest number and subtract the other smaller number. So, 6 - 2 = 4.
---Answer: The Number Family for 4, 2, and 6 includes: 4 + 2 = 6, 2 + 4 = 6, 6 - 4 = 2, and 6 - 2 = 4.

Why It Matters

Understanding number families helps you solve math problems faster and build a strong foundation for algebra and more complex calculations. It's useful for careers like a shopkeeper managing inventory, a chef adjusting recipes, or even a cricketer calculating runs needed to win.

Common Mistakes

MISTAKE: Students only write addition facts and forget the subtraction facts. | CORRECTION: Remember that a number family always includes two addition facts and two subtraction facts, making a total of four facts.

MISTAKE: Using numbers that don't belong together in the family (e.g., for 3, 5, 8, writing 3 + 4 = 7). | CORRECTION: Always check that the two smaller numbers add up to the largest number in your chosen family.

MISTAKE: Confusing the order in subtraction, like subtracting the larger number from the smaller one (e.g., 3 - 5 = ?). | CORRECTION: In a number family, subtraction always starts with the largest number.

Practice Questions

Try It Yourself

QUESTION: Write the complete number family for 5, 4, and 9. | ANSWER: 5 + 4 = 9, 4 + 5 = 9, 9 - 5 = 4, 9 - 4 = 5

QUESTION: If the numbers in a family are 7, 10, and 3, write all four related facts. | ANSWER: 7 + 3 = 10, 3 + 7 = 10, 10 - 7 = 3, 10 - 3 = 7

QUESTION: Your dad gave you Rs. 20 for snacks, and you spent Rs. 8 on a samosa. What are the three numbers in this family, and what are the four facts? | ANSWER: Numbers: 20, 8, 12. Facts: 8 + 12 = 20, 12 + 8 = 20, 20 - 8 = 12, 20 - 12 = 8

MCQ

Quick Quiz

Which set of facts correctly forms a number family for 6, 2, and 8?

6 + 2 = 8, 8 - 2 = 6, 8 - 6 = 2

6 + 2 = 8, 2 + 6 = 8, 8 - 6 = 2, 8 - 2 = 6

6 + 8 = 14, 8 - 6 = 2

2 + 8 = 10, 6 - 2 = 4

The Correct Answer Is:

Option B includes all four correct addition and subtraction facts for the numbers 6, 2, and 8. The other options are either incomplete or use incorrect number relationships.

Real World Connection

In the Real World

When you're checking your monthly mobile data usage, if you started with 10 GB and used 6 GB, you know 4 GB is left. This is a number family of 10, 6, and 4. You can quickly see how much you used, how much is left, or how much you started with if you know two of these values.

Key Vocabulary

Key Terms

ADDITION: Putting numbers together to find a total | SUBTRACTION: Taking one number away from another to find the difference | FACT: A true statement or equation in math | TOTAL: The result of adding numbers together

What's Next

What to Learn Next

Great job understanding number families! Next, you can explore 'Fact Families with Multiplication and Division.' This will show you how three numbers are related through multiplying and dividing, just like you saw with adding and subtracting.