What is a Number Family for 8?

S0-SA1-1220

Grade Level:

Pre-School – Class 2

All domains without exception

Definition

What is it?

A Number Family for 8 is a group of addition and subtraction facts that use the same three numbers to make 8. It shows how numbers are related through these operations. Think of it like a family where everyone is connected!

Simple Example

Quick Example

Imagine you have 8 laddoos. If your friend eats 3 laddoos, you are left with 5. This means 8 - 3 = 5. Also, if you had 3 laddoos and your friend gave you 5 more, you would have 8 (3 + 5 = 8). The numbers 3, 5, and 8 form a number family.

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 make 8? We know 2 + 6 = 8.
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Step 2: Now, flip the numbers in the addition. Does 6 + 2 also make 8? Yes, 6 + 2 = 8.
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Step 3: Move to subtraction. If we start with the biggest number, 8, and take away one of the smaller numbers (2), what do we get? 8 - 2 = 6.
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Step 4: Finally, start with 8 again and take away the other smaller number (6). What do we 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 solve math problems faster and makes mental calculations easier. It's super useful for careers like a shopkeeper managing stock, a cricket scorer calculating runs, or even a software developer working with numbers.

Common Mistakes

MISTAKE: Only writing addition facts for a number family. | CORRECTION: Remember to include both addition AND subtraction facts, as they are all related.

MISTAKE: Using numbers that don't add up to the target number (e.g., for 8, using 3 and 6). | CORRECTION: Always check if the two smaller numbers actually add up to the largest number in the family.

MISTAKE: Confusing the order of numbers in subtraction (e.g., writing 2 - 8 = 6). | CORRECTION: In subtraction, always start with the largest number in the family.

Practice Questions

Try It Yourself

QUESTION: Which of these is part of the Number Family for 8 using 4 and 4? A) 4 + 4 = 8 | B) 8 - 4 = 4 | C) Both A and B | ANSWER: C

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

QUESTION: Reema has 8 crayons. She gives 5 crayons to her brother. Write two subtraction facts and two addition facts that describe this situation and form a number family. | ANSWER: 8 - 5 = 3 (Reema has 3 left), 8 - 3 = 5 (She gave 5 away), 5 + 3 = 8 (Total crayons), 3 + 5 = 8 (Total crayons)

MCQ

Quick Quiz

Which set of facts correctly represents a Number Family for 8?

2 + 7 = 9, 9 - 2 = 7

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

4 + 3 = 7, 7 - 3 = 4

1 + 6 = 7, 7 - 1 = 6

The Correct Answer Is:

Option B correctly shows all four related facts (two addition, two subtraction) that use the numbers 3, 5, and 8. The other options do not add up to 8 or are incomplete.

Real World Connection

In the Real World

When you're calculating change after buying groceries at the local kirana store, you use number families. If an item costs 8 rupees and you pay with a 10-rupee note, you quickly calculate 10 - 8 = 2 rupees change. This is a part of the number family for 10 (8, 2, 10).

Key Vocabulary

Key Terms

Number Family: A group of related addition and subtraction facts using the same three numbers | Addition: Combining numbers to find a total | Subtraction: Taking one number away from another | Fact: A mathematical statement that is true

What's Next

What to Learn Next

Great job learning about number families! Next, you can explore 'Fact Families for Multiplication and Division'. This builds on the same idea, showing how multiplication and division are related, just like addition and subtraction.