What is a Number Fact for 20?

S0-SA1-0662

Grade Level:

Pre-School – Class 2

All domains without exception

Definition

What is it?

A 'number fact for 20' is any math sentence (like addition, subtraction, multiplication, or division) where the answer or result is 20. It helps us see different ways to make or break down the number 20. Think of it as knowing all the different combinations that lead to 20.

Simple Example

Quick Example

Imagine you need to score exactly 20 runs in a cricket match to win. If you scored 10 runs in the first over and then 10 runs in the second over, you've made 10 + 10 = 20 runs. This '10 + 10 = 20' is a number fact for 20.

Worked Example

Step-by-Step

Let's find some number facts for 20 using addition and subtraction.

Step 1: Start with addition. What two numbers add up to 20? Let's pick 15. So, 15 + ? = 20.
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Step 2: To find the missing number, we can count up from 15 to 20 (16, 17, 18, 19, 20 – that's 5 steps). Or, we can do 20 - 15.
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Step 3: 20 - 15 = 5.
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Step 4: So, 15 + 5 = 20 is an addition fact for 20.
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Step 5: Now, let's try subtraction. If you have 25 items and want to end up with 20, how many do you remove? 25 - ? = 20.
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Step 6: To find the missing number, we do 25 - 20.
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Step 7: 25 - 20 = 5.
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Step 8: So, 25 - 5 = 20 is a subtraction fact for 20.

Answer: Two number facts for 20 are 15 + 5 = 20 and 25 - 5 = 20.

Why It Matters

Understanding number facts helps you do mental math faster and solve problems without a calculator. This skill is super useful in careers like becoming a shopkeeper calculating change, a data analyst working with numbers, or even an engineer designing structures that need precise measurements.

Common Mistakes

MISTAKE: Confusing number facts for 20 with multiplication tables of 20. For example, saying '2 x 10 = 20' is a fact for 20, but '2 x 20 = 40' is not. | CORRECTION: Always check if the final answer or result of your math sentence is exactly 20. If it's not 20, it's not a number fact FOR 20.

MISTAKE: Only thinking about addition facts. Students often forget that subtraction, multiplication, and division can also result in 20. | CORRECTION: Remember to explore all four basic operations (addition, subtraction, multiplication, division) when looking for number facts for 20.

MISTAKE: Writing down '20' as part of the equation but not as the result. For example, '20 + 5 = 25'. Here, 20 is used, but 25 is the result. | CORRECTION: Ensure that the number 20 is the answer to the mathematical operation you are performing. For example, '18 + 2 = 20'.

Practice Questions

Try It Yourself

QUESTION: What is an addition fact for 20 if one of the numbers is 12? | ANSWER: 12 + 8 = 20

QUESTION: Find a division fact for 20 using the number 4. | ANSWER: 80 / 4 = 20

QUESTION: A chaiwala sells tea for ₹10 per cup. How many cups must he sell to earn exactly ₹20? Write this as a multiplication fact for 20. | ANSWER: 2 x 10 = 20 (or 10 x 2 = 20)

MCQ

Quick Quiz

Which of the following is NOT a number fact for 20?

10 + 10 = 20

25 - 5 = 20

4 x 5 = 20

20 + 3 = 23

The Correct Answer Is:

Options A, B, and C all result in 20, making them number facts for 20. Option D results in 23, not 20, so it is not a number fact for 20.

Real World Connection

In the Real World

When you're buying snacks at the local kirana store, you often use number facts. If a packet of biscuits costs ₹5 and you want to buy enough to spend exactly ₹20, you quickly calculate '4 x 5 = 20' to know you can buy 4 packets. This quick calculation uses a multiplication fact for 20.

Key Vocabulary

Key Terms

Number Fact: A mathematical sentence where the answer is a specific number. | Addition: Combining two or more numbers. | Subtraction: Taking one number away from another. | Multiplication: Repeated addition. | Division: Sharing equally or grouping.

What's Next

What to Learn Next

Great job learning about number facts for 20! Next, you can explore 'Number Facts for 50' or 'Number Facts for 100'. This will help you become even faster and more confident with bigger numbers, building on the skills you've just learned.