What is a Number Family for 13?

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Grade Level:

Pre-School – Class 2

All domains without exception

Definition

What is it?

A Number Family for a specific number, like 13, is a group of addition and subtraction facts that use the same three numbers. It shows how these three numbers are related through basic operations. For 13, it means finding two numbers that add up to 13, and then forming all possible addition and subtraction sentences with them.

Simple Example

Quick Example

Imagine you have 13 ladoos. If you give 5 ladoos to your friend, you are left with 8 ladoos. This means 5 + 8 = 13 and 13 - 5 = 8. Also, if you had 8 ladoos and your friend gave you 5 more, you'd have 13. So, the numbers 5, 8, and 13 form a number family.

Worked Example

Step-by-Step

Let's find a Number Family for 13 using the numbers 6 and 7.

Step 1: Identify two numbers that add up to 13. We choose 6 and 7, because 6 + 7 = 13.

Step 2: Write the first addition fact. 6 + 7 = 13.

Step 3: Write the second addition fact by swapping the order of the first two numbers. 7 + 6 = 13.

Step 4: Write the first subtraction fact. Start with the largest number (13) and subtract one of the smaller numbers (6). 13 - 6 = 7.

Step 5: Write the second subtraction fact. Start with the largest number (13) and subtract the other smaller number (7). 13 - 7 = 6.

Answer: The Number Family for 13 using 6 and 7 is: 6 + 7 = 13, 7 + 6 = 13, 13 - 6 = 7, 13 - 7 = 6.

Why It Matters

Understanding number families helps you solve math problems faster and build a strong foundation for algebra. It's like knowing different routes to reach the same destination! This skill is useful for careers in finance, like a bank manager, or even for engineers who need to quickly calculate quantities.

Common Mistakes

MISTAKE: Using numbers that don't add up to the target number. For example, saying 4 and 8 are part of 13's number family (4+8=12, not 13). | CORRECTION: Always check that the two smaller numbers add up to the main number.

MISTAKE: Mixing up the numbers in subtraction. For example, writing 6 - 13 = 7. | CORRECTION: In subtraction for number families, always start with the largest number (the sum) and subtract one of the smaller numbers.

MISTAKE: Forgetting one of the four facts. For example, only writing 6+7=13 and 13-6=7. | CORRECTION: Remember there are usually two addition facts and two subtraction facts in a complete number family (unless the two smaller numbers are the same, like 6+6=12).

Practice Questions

Try It Yourself

QUESTION: Write the complete number family for 13 using the numbers 4 and 9. | ANSWER: 4 + 9 = 13, 9 + 4 = 13, 13 - 4 = 9, 13 - 9 = 4

QUESTION: If you know that 13 - 8 = 5, what are the other three facts in this number family? | ANSWER: 13 - 5 = 8, 8 + 5 = 13, 5 + 8 = 13

QUESTION: A vegetable seller has 13 tomatoes. He sells some and is left with 7 tomatoes. What number family describes this situation? Write all four facts. | ANSWER: The numbers are 6, 7, and 13. The number family is: 6 + 7 = 13, 7 + 6 = 13, 13 - 6 = 7, 13 - 7 = 6

MCQ

Quick Quiz

Which set of facts forms a complete number family for 13?

A) 5 + 8 = 13, 13 - 5 = 8

B) 6 + 7 = 13, 7 + 6 = 13, 13 - 6 = 7, 13 - 7 = 6

C) 13 + 0 = 13, 13 - 13 = 0

D) 13 - 3 = 10, 10 + 3 = 13

The Correct Answer Is:

Option B shows all four related addition and subtraction facts using the numbers 6, 7, and 13. The other options are incomplete or do not form a proper number family.

Real World Connection

In the Real World

When you count change after buying snacks, you're using number families! If your chai costs 7 rupees and you give the vendor 10 rupees, you expect 3 rupees back (10 - 7 = 3). This connects to the number family of 10 (7 + 3 = 10). Similarly, when splitting a bill among friends or calculating cricket scores, these relationships are constantly used.

Key Vocabulary

Key Terms

ADDITION: Combining two or more numbers to get a total | SUBTRACTION: Taking one number away from another to find the difference | NUMBER FAMILY: A group of related addition and subtraction facts using the same three numbers | SUM: The result of adding two or more numbers

What's Next

What to Learn Next

Great job understanding number families! Next, you can explore 'Fact Families for Multiplication and Division'. It builds on the same idea of related operations, but with multiplying and dividing numbers. This will make understanding times tables much easier!