What is a Number Family (of 8)?

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Grade Level:

Pre-School – Class 2

All domains without exception

Definition

What is it?

A Number Family (of 8) is a group of related addition and subtraction facts that use the same three numbers. For the number 8, it means finding pairs of numbers that add up to 8, and then using those numbers to create subtraction facts.

Simple Example

Quick Example

Imagine you have 8 ladoos. You can put 5 ladoos in one box and 3 ladoos in another. This shows 5 + 3 = 8. If you eat the 3 ladoos, you are left with 5, so 8 - 3 = 5. This is part of the 'Number Family of 8' using 5, 3, and 8.

Worked Example

Step-by-Step

Let's find the Number Family for 8 using the numbers 2, 6, and 8.

Step 1: Start with addition. How can 2 and 6 add up to 8? Write it down.
2 + 6 = 8

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Step 2: Now, reverse the order of the first two numbers. Does it still add up to 8? Yes.
6 + 2 = 8

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Step 3: Now, use subtraction. Start with the total (8) and subtract one of the smaller numbers (2). What do you get?
8 - 2 = 6

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Step 4: Finally, start with the total (8) again and subtract the other smaller number (6). What do you get?
8 - 6 = 2

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Answer: The Number Family for 8 using 2, 6, and 8 is: 2 + 6 = 8, 6 + 2 = 8, 8 - 2 = 6, and 8 - 6 = 2.

Why It Matters

Understanding number families helps you quickly solve addition and subtraction problems without counting on your fingers. It builds a strong foundation for mental math and algebra. This skill is crucial for careers like a shopkeeper managing inventory or a data analyst working with numbers every day.

Common Mistakes

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

MISTAKE: Using numbers that don't add up to the 'family' number (e.g., for 'Family of 8', using 3 + 4 = 7). | CORRECTION: Always ensure your two smaller numbers sum up exactly to the target family number.

MISTAKE: Confusing the order in subtraction, like writing 2 - 8 = 6. | CORRECTION: In subtraction for number families, always start with the largest number (the 'family' number) and subtract one of the smaller numbers.

Practice Questions

Try It Yourself

QUESTION: Write the Number Family for 8 using the numbers 7, 1, and 8. | ANSWER: 7 + 1 = 8, 1 + 7 = 8, 8 - 1 = 7, 8 - 7 = 1

QUESTION: If you know 4 + 4 = 8, what are the other facts in this Number Family? | ANSWER: 4 + 4 = 8, 8 - 4 = 4 (Note: There are only two distinct facts when the two smaller numbers are the same).

QUESTION: A vegetable seller has 8 tomatoes. He sells some and is left with 3. What is the Number Family that describes this situation? | ANSWER: 5 + 3 = 8, 3 + 5 = 8, 8 - 3 = 5, 8 - 5 = 3 (He sold 5 tomatoes).

MCQ

Quick Quiz

Which set of facts correctly represents a Number Family for 8 using the numbers 3, 5, and 8?

3 + 5 = 8, 5 + 3 = 8, 8 - 3 = 5, 8 - 5 = 3

3 + 5 = 8, 8 - 5 = 3, 5 + 3 = 8, 8 + 3 = 11

8 - 3 = 5, 5 - 3 = 2, 3 + 5 = 8

3 + 5 = 8, 8 - 3 = 5, 8 - 5 = 3, 5 + 8 = 13

The Correct Answer Is:

Option A correctly lists all four related addition and subtraction facts using only the numbers 3, 5, and 8. The other options include incorrect operations or numbers not part of the family.

Real World Connection

In the Real World

When you are sharing a packet of 8 biscuits with your friends, you can use number families. If you give 4 to one friend, you immediately know you have 4 left for another friend (8 - 4 = 4). Or if you want to give 2 to one and 6 to another, you know it sums up to 8 (2 + 6 = 8). This helps in fair distribution and quick calculations in daily life.

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 set 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 other numbers like 9 or 10. This will strengthen your understanding and make you super fast at mental math, which is a key skill for more advanced topics like algebra.