What are Friendly Numbers? | Simple Explanation for Class 1-2

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What is a Friendly Number?

Grade Level:

Pre-School – Class 2

All domains without exception

Definition

What is it?

A Friendly Number is a concept in math that deals with very large numbers and their divisors. It's about finding pairs of numbers where the sum of the divisors of one number (excluding itself) is related to the other number in a special ratio. However, for your class level (Pre-School - Class 2), 'Friendly Numbers' usually refers to numbers that are easy to add or subtract to make a round number like 10, 20, or 100.

Simple Example

Quick Example

Imagine you have 7 marbles and your friend has 3 marbles. If you put them together, you get 10 marbles. Here, 7 and 3 are 'friendly numbers' because they easily add up to a round number (10). It's like finding numbers that are good partners for easy counting!

Worked Example

Step-by-Step

Let's say you have 6 ladoos and want to make a total of 10 ladoos. How many more ladoos do you need?

1. Start with the number of ladoos you have: 6
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2. Think about the target round number: 10
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3. Count up from 6 to 10: 7, 8, 9, 10
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4. The numbers you counted are 4 (one for each finger or step).
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5. So, 6 and 4 are 'friendly numbers' because they add up to 10.
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ANSWER: You need 4 more ladoos.

Why It Matters

Understanding friendly numbers helps you do mental math faster, like quickly calculating change at a shop or adding scores in a game. It builds a strong foundation for understanding number relationships, which is useful in careers like finance, engineering, and even game development.

Common Mistakes

MISTAKE: Thinking friendly numbers always add up to 10. | CORRECTION: Friendly numbers can add up to any round number like 10, 20, 50, or 100. The idea is to make calculations easier.

MISTAKE: Only thinking about addition. | CORRECTION: Friendly numbers can also be used for easy subtraction. For example, to subtract 7 from 10, you know the 'friendly number' 3 is the answer.

MISTAKE: Confusing 'friendly numbers' with 'even' or 'odd' numbers. | CORRECTION: Friendly numbers are about pairs that make round totals, not whether a number can be divided by 2 or not.

Practice Questions

Try It Yourself

QUESTION: What number is friendly with 8 to make 10? | ANSWER: 2

QUESTION: If you have 15 crayons, what number is friendly with 15 to make 20? | ANSWER: 5

QUESTION: Your mom gave you 7 rupees, and your dad gave you 3 rupees. How much money do you have in total? Are 7 and 3 friendly numbers for a round total? | ANSWER: You have 10 rupees in total. Yes, 7 and 3 are friendly numbers for 10.

MCQ

Quick Quiz

Which pair of numbers are friendly to make 10?

2 and 6

4 and 5

1 and 9

3 and 6

The Correct Answer Is:

1 and 9 add up to 10, making them 'friendly' for this round number. The other pairs do not add up to 10.

Real World Connection

In the Real World

When you pay for something at a local kirana store, and the shopkeeper quickly gives you change, they often use 'friendly numbers' in their head. For example, if an item costs 17 rupees and you give 20 rupees, they know 17 and 3 are friendly numbers for 20, so they give you 3 rupees back quickly.

Key Vocabulary

Key Terms

ADDITION: Putting numbers together | SUBTRACTION: Taking one number away from another | ROUND NUMBER: Numbers like 10, 20, 100 that end in zero and are easy to work with | PAIR: Two things that go together

What's Next

What to Learn Next

Great job learning about friendly numbers! Next, you can explore 'Number Bonds' which is a similar concept about how numbers break apart and come together. This will further strengthen your mental math skills and make you a number wizard!