What is a Number Fact for 18?

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Grade Level:

Pre-School – Class 2

All domains without exception

Definition

What is it?

A 'number fact' for a number like 18 is a simple math sentence that shows how different numbers combine to make 18. These facts can be about addition, subtraction, multiplication, or division. They help us understand the relationships between numbers.

Simple Example

Quick Example

Imagine you have 18 laddoos. If you give 10 laddoos to your friend and keep 8 for yourself, then '10 + 8 = 18' is an addition fact for 18. Similarly, if you started with 18 laddoos and ate 5, leaving 13, then '18 - 5 = 13' is a subtraction fact for 18.

Worked Example

Step-by-Step

Let's find some number facts for 18 using different operations.

Step 1: Addition. We need two numbers that add up to 18. Let's pick 9 and 9. So, 9 + 9 = 18 is an addition fact.
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Step 2: Subtraction. We need to start with 18 and subtract a number to get another number. Let's say we subtract 6 from 18. So, 18 - 6 = 12 is a subtraction fact.
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Step 3: Multiplication. We need two numbers that multiply to 18. Let's pick 2 and 9. So, 2 x 9 = 18 is a multiplication fact.
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Step 4: Division. We need to divide 18 by a number to get another number. Let's divide 18 by 3. So, 18 / 3 = 6 is a division fact.

Answer: Some number facts for 18 are 9 + 9 = 18, 18 - 6 = 12, 2 x 9 = 18, and 18 / 3 = 6.

Why It Matters

Understanding number facts is crucial for building a strong foundation in math. It helps you do mental calculations faster and solve bigger problems easily. This skill is useful for careers like accountants who manage money, engineers who design structures, and even shopkeepers who calculate bills quickly.

Common Mistakes

MISTAKE: Only thinking of addition facts for a number. | CORRECTION: Remember that number facts include addition, subtraction, multiplication, and division.

MISTAKE: Confusing number facts with factors. For example, saying 4 is a number fact for 18 because it's part of 18 - 4 = 14. | CORRECTION: A number fact is the *entire equation* (e.g., 18 - 4 = 14), not just one number within it. Factors are numbers that divide another number exactly (like 2, 3, 6, 9 are factors of 18).

MISTAKE: Not checking if the equation actually equals the target number. For example, saying 10 + 7 = 18 is a fact for 18. | CORRECTION: Always verify that the operation (addition, subtraction, etc.) results in the given number. 10 + 7 equals 17, not 18.

Practice Questions

Try It Yourself

QUESTION: Write an addition fact for 18 using the number 5. | ANSWER: 5 + 13 = 18

QUESTION: Find a multiplication fact for 18 using a number greater than 5. | ANSWER: 3 x 6 = 18 (or 6 x 3 = 18 or 9 x 2 = 18 or 2 x 9 = 18)

QUESTION: If you have 18 cricket balls and want to divide them equally among 3 friends, how many balls does each friend get? Write this as a division fact for 18. | ANSWER: 18 / 3 = 6. Each friend gets 6 balls.

MCQ

Quick Quiz

Which of these is NOT a number fact for 18?

18 - 7 = 11

10 + 8 = 18

4 x 5 = 18

18 / 2 = 9

The Correct Answer Is:

Options A, B, and D all correctly show how numbers relate to 18. Option C, '4 x 5 = 18', is incorrect because 4 multiplied by 5 equals 20, not 18.

Real World Connection

In the Real World

When a shopkeeper calculates the total cost of items, they are using addition facts. For instance, if a packet of biscuits costs Rs 10 and a packet of chips costs Rs 8, the total bill is Rs 18, which is 10 + 8 = 18. Similarly, managing your pocket money or dividing sweets among family members uses these basic number facts.

Key Vocabulary

Key Terms

ADDITION: Combining numbers to find a total | SUBTRACTION: Taking one number away from another | MULTIPLICATION: Repeated addition of the same number | DIVISION: Splitting a number into equal parts | NUMBER FACT: A basic mathematical equation showing relationships for a specific number

What's Next

What to Learn Next

Now that you understand number facts for single numbers, you can explore number families and fact families. These concepts will show you how addition and subtraction (or multiplication and division) are related, making your math skills even stronger!