Calculate the Product: 1.23 × 180 Decimal Multiplication

Q: Why do I ignore the decimal point when multiplying?

Ignoring the decimal initially makes the multiplication much easier! You multiply $ 123 \times 180 $ like regular whole numbers, then add the decimal back at the end.

Q: How do I know where to put the decimal point?

Count the total decimal places in both numbers you're multiplying. $ 1.23 $ has 2 decimal places, $ 180 $ has 0, so your answer needs 2 decimal places.

Q: What if my answer ends in zero after the decimal?

You can drop trailing zeros! $ 221.40 $ becomes $ 221.4 $. But be careful - don't drop zeros that aren't at the very end.

Q: Is there a faster way to multiply by 180?

Yes! Think of 180 as $ 18 \times 10 $. First calculate $ 1.23 \times 18 = 22.14 $, then multiply by 10 to get $ 221.4 $.

Q: How can I check if 221.4 is correct?

Use estimation! $ 1.23 $ is close to 1.2, and $ 1.2 \times 180 = 216 $. Since 221.4 is close to 216, your answer makes sense!

Decimal Multiplication with Whole Numbers

$1.23\times180=$

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations

00:00 Solve

00:03 Multiply each digit by each digit, and place in the appropriate position

00:09 Any number multiplied by 0 always equals 0

00:17 Move to the next digit, calculate and place in the appropriate position

00:23 Calculate and place, add the tens digit when necessary

00:47 Move to the next digit, calculate and place in the appropriate position

00:52 Any number multiplied by 1 always equals itself

01:00 Combine the results

01:08 Sum up all the digits after the decimal point

01:14 Based on this sum, place the decimal point

01:23 And this is the solution to the problem

Step-by-step written solution

Follow each step carefully to understand the complete solution

Understand the problem

$1.23\times180=$

Step-by-step solution

To solve this problem, we'll follow these steps:

Step 1: Multiply the numbers.
Step 2: Consider the decimal places.

Let's go through each step:
Step 1: We start by calculating the product of $1.23$ and $180$ . Multiplying the numbers without considering the decimal initially, we treat it as $123 \times 180$ .
Step 2: Calculate $123 \times 180$ . This can be split into simpler calculations, $123 \times (100 + 80)$ :
- $123 \times 100 = 12300$
- $123 \times 80 = 9840$
Adding these: $12300 + 9840 = 22140$ .
Since $1.23$ has two decimal places, we place the decimal point back in the product, which gives us $221.40$ , or simplified, $221.4$ .

Therefore, the solution to the problem is $221.4$ .

Final Answer

$221.4$

Key Points to Remember

Essential concepts to master this topic

Decimal Rule: Count decimal places in factors to position result
Technique: Multiply $123 \times 180 = 22140$ then place decimal
Check: Verify $1.23$ has 2 decimals gives $221.40$ ✓

Common Mistakes

Avoid these frequent errors

Forgetting to count decimal places
Don't just multiply 123 × 180 = 22140 and stop there! This gives 22140 instead of 221.4. Always count decimal places in the original numbers (1.23 has 2 places) and place the decimal point correctly in your final answer.

Practice Quiz

Test your knowledge with interactive questions

$\text{0}.07\times10=$

FAQ

Everything you need to know about this question

Why do I ignore the decimal point when multiplying?

Ignoring the decimal initially makes the multiplication much easier! You multiply $123 \times 180$ like regular whole numbers, then add the decimal back at the end.

How do I know where to put the decimal point?

Count the total decimal places in both numbers you're multiplying. $1.23$ has 2 decimal places, $180$ has 0, so your answer needs 2 decimal places.

What if my answer ends in zero after the decimal?

You can drop trailing zeros! $221.40$ becomes $221.4$ . But be careful - don't drop zeros that aren't at the very end.

Is there a faster way to multiply by 180?

Yes! Think of 180 as $18 \times 10$ . First calculate $1.23 \times 18 = 22.14$ , then multiply by 10 to get $221.4$ .

How can I check if 221.4 is correct?

Use estimation! $1.23$ is close to 1.2, and $1.2 \times 180 = 216$ . Since 221.4 is close to 216, your answer makes sense!

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