Solve Decimal Addition: 0.1 + 0.2 Step-by-Step

Q: Why can't I just add 1 + 2 = 3?

Because 0.1 means 1 tenth, not 1 whole! When you ignore the decimal points, you're adding 1 whole + 2 wholes = 3 wholes, which is completely different from adding tenths.

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

The decimal point in your answer goes in the same column as the decimal points in the numbers you're adding. Think of it as staying in the same vertical line!

Q: What if the decimal numbers have different lengths?

Add trailing zeros to make them the same length! For example, treat 0.1 as 0.10 when adding to 0.25. This makes alignment easier.

Q: Is 0.3 the same as .3?

Yes! Both represent 3 tenths. However, writing 0.3 with the leading zero is clearer and helps prevent mistakes when reading decimal numbers.

Q: Can I check my answer using fractions?

Absolutely! $ 0.1 = \frac{1}{10} $ and $ 0.2 = \frac{2}{10} $, so $ \frac{1}{10} + \frac{2}{10} = \frac{3}{10} = 0.3 $ ✓

Decimal Addition with Tenths Place Values

Solve the following:

$0.1+0.2=$

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations

00:05 Let's solve this with vertical addition.

00:09 First, write the numbers one below the other.

00:13 Make sure each digit lines up nicely.

00:17 Start by adding the digits in the rightmost column.

00:21 Calculate, and put the result below the line.

00:25 Keep adding, calculate each step, and write it down.

00:35 Great job! That's how you find the solution.

Step-by-step written solution

Follow each step carefully to understand the complete solution

Understand the problem

Solve the following:

$0.1+0.2=$

Step-by-step solution

To solve this problem, let's perform the addition of the two decimal numbers $0.1$ and $0.2$ step-by-step.

Step 1: Align the decimal points of the numbers.

We write the numbers as:

$0.1$

$+0.2$

Here, the decimal points are already aligned.

Step 2: Add the numbers column by column starting from the rightmost side, which is the decimal fraction part.

$0.1$ consists of 1 in the tenths place, and $0.2$ consists of 2 in the tenths place. By adding these:

$0.1 + 0.2 = 0.3$

Thus, the sum of $0.1$ and $0.2$ is $0.3$ .

Looking at the answer choices, the correct choice is:

Choice 2: $0.3$

Therefore, the solution to the problem is $0.3$ .

Final Answer

0.3

Key Points to Remember

Essential concepts to master this topic

Alignment: Line up decimal points vertically before adding numbers
Technique: Add column by column: 0.1 + 0.2 = 0.3
Check: Count decimal places: both addends have 1, answer has 1 ✓

Common Mistakes

Avoid these frequent errors

Adding digits without aligning decimal points
Don't just add 1 + 2 = 3 ignoring decimal placement = wrong answer of 3 instead of 0.3! This treats decimals like whole numbers and misses the place value. Always align decimal points first, then add column by column.

Practice Quiz

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FAQ

Everything you need to know about this question

Why can't I just add 1 + 2 = 3?

Because 0.1 means 1 tenth, not 1 whole! When you ignore the decimal points, you're adding 1 whole + 2 wholes = 3 wholes, which is completely different from adding tenths.

How do I know where to put the decimal point in my answer?

The decimal point in your answer goes in the same column as the decimal points in the numbers you're adding. Think of it as staying in the same vertical line!

What if the decimal numbers have different lengths?

Add trailing zeros to make them the same length! For example, treat 0.1 as 0.10 when adding to 0.25. This makes alignment easier.

Is 0.3 the same as .3?

Yes! Both represent 3 tenths. However, writing 0.3 with the leading zero is clearer and helps prevent mistakes when reading decimal numbers.

Can I check my answer using fractions?

Absolutely! $0.1 = \frac{1}{10}$ and $0.2 = \frac{2}{10}$ , so $\frac{1}{10} + \frac{2}{10} = \frac{3}{10} = 0.3$ ✓

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