What is Multiplying by 100?

S1-SA1-0111

Grade Level:

Class 3

Maths, Computing, Place Value

Definition

What is it?

Multiplying by 100 means you are taking a number and making it 100 times bigger. It's like having 100 groups of that same number. The quickest way to multiply by 100 is to add two zeros to the end of the original number.

Simple Example

Quick Example

Imagine you have 5 cricket balls. If you multiply 5 by 100, it means you now have 100 times more cricket balls, which is 500 cricket balls. It's like having 100 friends, and each friend gives you 5 balls.

Worked Example

Step-by-Step

Let's multiply 12 by 100.

Step 1: Start with the number 12.

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Step 2: When multiplying by 100, we know we need to add two zeros to the end of the number.

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Step 3: Take the number 12 and write it down.

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Step 4: Add two zeros (00) to the right side of 12.

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Step 5: The new number formed is 1200.

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Answer: So, 12 x 100 = 1200.

Why It Matters

Understanding multiplication by 100 is key for place value and mental math. It's super useful for calculating percentages, converting currency, and even in computer programming for scaling values. Future engineers, business owners, and scientists use this concept daily!

Common Mistakes

MISTAKE: Adding only one zero instead of two (e.g., 7 x 100 = 70). | CORRECTION: Remember that 100 has two zeros, so you must add exactly two zeros to the end of the number.

MISTAKE: Forgetting to carry over when multiplying larger numbers (e.g., trying to do 25 x 100 by just adding zeros, but getting confused with the 5). | CORRECTION: The 'add two zeros' rule works for any whole number. Just write the number and then '00'. For decimals, the decimal point shifts two places to the right.

MISTAKE: Confusing multiplying by 100 with dividing by 100. | CORRECTION: Multiplying makes the number bigger (adding zeros), while dividing makes it smaller (removing zeros or shifting decimal left).

Practice Questions

Try It Yourself

QUESTION: What is 9 multiplied by 100? | ANSWER: 900

QUESTION: A shopkeeper sells a pen for ₹15. If he sells 100 such pens, how much money does he collect? | ANSWER: ₹1500

QUESTION: If a car travels 65 kilometers in one hour, how many kilometers would it travel in 100 hours at the same speed? | ANSWER: 6500 kilometers

MCQ

Quick Quiz

Which of these is the correct way to calculate 23 x 100?

Add one zero to 23 to get 230

Add two zeros to 23 to get 2300

Multiply 23 by 10 and then add 100

Divide 23 by 100

The Correct Answer Is:

When multiplying by 100, you simply write the original number and then add two zeros to its right side. So, 23 becomes 2300. Options A, C, and D are incorrect methods for multiplying by 100.

Real World Connection

In the Real World

When you check your mobile data usage, sometimes it's shown in MB and you need to convert it to KB. 1 MB is 1024 KB, which is close to 1000. Similarly, when a bank calculates simple interest on your savings, they often use percentages, which means multiplying your money by a fraction of 100. Or, when you buy 100 items of the same price, you quickly multiply the price by 100 to find the total.

Key Vocabulary

Key Terms

MULTIPLY: To combine equal groups or find the total number of items in equal groups | PRODUCT: The answer to a multiplication problem | PLACE VALUE: The value of each digit in a number based on its position | ZEROES: The digit 0, used here to show powers of ten

What's Next

What to Learn Next

Now that you've mastered multiplying by 100, try learning about multiplying by 1000! It builds directly on this concept, just with one extra zero. You'll be a multiplication wizard in no time!