What is a Fact Family for 5?

S0-SA1-0380

Grade Level:

Pre-School – Class 2

All domains without exception

Definition

What is it?

A Fact Family for 5 is a group of related addition and subtraction sentences that use the same three numbers. For the number 5, it means finding pairs of numbers that add up to 5, and then showing how those numbers are connected through addition and subtraction.

Simple Example

Quick Example

Imagine you have 5 delicious ladoos. You can split them in different ways. If you have 2 ladoos in one hand and 3 in the other, that makes 5. So, 2 + 3 = 5. This also means 3 + 2 = 5. And if you start with 5 ladoos and eat 2, you have 3 left (5 - 2 = 3). If you eat 3, you have 2 left (5 - 3 = 2). These four sentences form a fact family for 5.

Worked Example

Step-by-Step

Let's find the fact family for the numbers 2, 3, and 5.

Step 1: Identify the two smaller numbers that add up to the largest number. Here, 2 and 3 add up to 5.

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Step 2: Write the first addition sentence. Put the two smaller numbers together. So, 2 + 3 = 5.

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Step 3: Write the second addition sentence. Just swap the order of the smaller numbers. So, 3 + 2 = 5.

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Step 4: Write the first subtraction sentence. Start with the largest number (5) and subtract one of the smaller numbers (2). So, 5 - 2 = 3.

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Step 5: Write the second subtraction sentence. Start with the largest number (5) and subtract the other smaller number (3). So, 5 - 3 = 2.

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Answer: The fact family for 2, 3, and 5 is: 2 + 3 = 5, 3 + 2 = 5, 5 - 2 = 3, and 5 - 3 = 2.

Why It Matters

Understanding fact families helps you see how numbers are related, making mental math much faster. This skill is crucial for everyday tasks like calculating change at a shop or splitting bills with friends. It's a foundational concept for careers in finance, engineering, or even managing a small business.

Common Mistakes

MISTAKE: Only writing addition sentences for a fact family. | CORRECTION: Remember that a complete fact family includes both addition and subtraction sentences using the same three numbers.

MISTAKE: Using different numbers in the subtraction sentences than the ones used in addition. | CORRECTION: Always use only the three numbers from the fact family. For example, if the numbers are 2, 3, and 5, don't use 4 or 1 in your sentences.

MISTAKE: Confusing the largest number with the smaller numbers in subtraction. | CORRECTION: In subtraction for a fact family, you always start with the largest number and subtract one of the smaller numbers to get the other smaller number.

Practice Questions

Try It Yourself

QUESTION: Write the fact family for the numbers 1, 4, and 5. | ANSWER: 1 + 4 = 5, 4 + 1 = 5, 5 - 1 = 4, 5 - 4 = 1

QUESTION: If you know 5 - 0 = 5, what are the other three sentences in this fact family? | ANSWER: 0 + 5 = 5, 5 + 0 = 5, 5 - 5 = 0

QUESTION: A vegetable vendor sold 5 kg of potatoes. If he sold 2 kg in the morning, how much did he sell in the afternoon? Write the fact family for this situation. | ANSWER: 2 + 3 = 5, 3 + 2 = 5, 5 - 2 = 3, 5 - 3 = 2. (He sold 3 kg in the afternoon.)

MCQ

Quick Quiz

Which of these is NOT part of the fact family for 2, 3, and 5?

2 + 3 = 5

5 - 3 = 2

3 + 2 = 5

5 - 2 = 4

The Correct Answer Is:

Options A, B, and C correctly use the numbers 2, 3, and 5 in addition and subtraction. Option D is incorrect because 5 - 2 equals 3, not 4. It does not belong to the fact family of 2, 3, and 5.

Real World Connection

In the Real World

When you're tracking your daily mobile data usage, you use fact families. If you have a 5 GB pack and have already used 2 GB, you instantly know you have 3 GB left (5 - 2 = 3). This helps you manage your data efficiently, just like how many apps show you 'data remaining' based on simple calculations.

Key Vocabulary

Key Terms

FACT FAMILY: A group of related addition and subtraction sentences using the same three numbers. | ADDITION: Combining two or more numbers to find their total sum. | SUBTRACTION: Taking one number away from another to find the difference. | RELATED SENTENCES: Mathematical statements that are connected because they use the same set of numbers. | SUM: The result of an addition.

What's Next

What to Learn Next

Great job understanding fact families for 5! Next, you can explore fact families for other numbers like 10 or 20. This will help you build a stronger foundation in addition and subtraction, making you super fast with calculations!