What is Multiplying by Eight?

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Grade Level:

Pre-School – Class 2

All domains without exception

Definition

What is it?

Multiplying by eight means adding the same number eight times. It's a quick way to count groups of eight or find the total when you have eight equal sets of something. Think of it as repeated addition where the number 8 is added again and again.

Simple Example

Quick Example

Imagine you have 8 friends, and each friend has 5 lollipops. To find the total number of lollipops, you can multiply 5 by 8. This tells you that 5 lollipops, taken 8 times, gives you a grand total.

Worked Example

Step-by-Step

Let's find out how much 8 packets of biscuits cost if each packet is Rs 12.
1. Identify the numbers: We have 8 packets and each costs Rs 12.
2. Understand the operation: We need to find the total cost, so we multiply.
3. Set up the multiplication: 12 x 8.
4. Multiply the ones place: 2 x 8 = 16. Write down 6 and carry over 1.
5. Multiply the tens place: 1 x 8 = 8. Add the carried over 1: 8 + 1 = 9.
6. Combine the results: The answer is 96.
So, 8 packets of biscuits will cost Rs 96.

Why It Matters

Understanding multiplication by eight is a fundamental skill that builds your mathematical speed and accuracy. It's crucial for everyday calculations, like figuring out how many ladoos you need for 8 guests or calculating distances in science. Future careers in engineering, finance, or even running a small business will rely on quick mental math skills like this.

Common Mistakes

MISTAKE: Adding 8 to the number instead of multiplying by 8 (e.g., 5 x 8 = 5 + 8 = 13) | CORRECTION: Remember multiplication is repeated addition. 5 x 8 means 5 added 8 times (5 + 5 + 5 + 5 + 5 + 5 + 5 + 5), not just 5 + 8.

MISTAKE: Forgetting the carry-over when multiplying larger numbers (e.g., 12 x 8 = 86 instead of 96) | CORRECTION: Always remember to carry over any tens or hundreds when multiplying digits, and add them to the next product.

MISTAKE: Confusing the multiplication tables for 7 or 9 with 8 (e.g., saying 8 x 7 = 56, but writing 8 x 7 = 63) | CORRECTION: Practice the 8 times table regularly. Use flashcards or skip counting to memorize it correctly.

Practice Questions

Try It Yourself

QUESTION: If an auto-rickshaw travels 8 km every day, how many kilometers does it travel in 5 days? | ANSWER: 40 km

QUESTION: A gardener plants 15 saplings in each row. If he plants 8 such rows, how many saplings did he plant in total? | ANSWER: 120 saplings

QUESTION: Your school has 8 classrooms. If each classroom has 25 students, and each student needs 3 notebooks, how many notebooks are needed for all the students in one classroom? (Hint: First find students in one classroom, then multiply by notebooks per student.) | ANSWER: 75 notebooks

MCQ

Quick Quiz

What is the product of 8 and 7?

The Correct Answer Is:

The product of 8 and 7 means 8 multiplied by 7. Counting 7 eight times or 8 seven times gives 56. Options A, C, and D are incorrect values.

Real World Connection

In the Real World

When you buy groceries, suppose you need 8 packets of atta (flour) for the month, and each packet costs Rs 50. To quickly calculate the total bill for atta, you'd multiply 50 by 8. Similarly, a cricket analyst might multiply a player's average runs by 8 to estimate their score in 8 matches.

Key Vocabulary

Key Terms

MULTIPLY: To combine equal groups to find a total | PRODUCT: The answer you get when you multiply two or more numbers | TIMES TABLE: A list of the results of multiplying a particular number by other numbers | REPEATED ADDITION: Adding the same number multiple times, which is what multiplication does

What's Next

What to Learn Next

Great job understanding multiplication by eight! Now that you've mastered this, you're ready to learn about the multiplication table of 9. It builds directly on your current knowledge and will make you even faster at mental math!