Calculate the Sum: Solving 10.1 + 2.3 Step by Step

Decimal Addition with Tenths Place Alignment

10.1+2.3= \text{10}.1+2.3=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve
00:03 We will use long addition for calculation
00:08 Place the decimal point in the appropriate position
00:11 We'll start by adding the smallest appropriate digits
00:14 We'll place and continue to add and calculate
00:25 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

10.1+2.3= \text{10}.1+2.3=

2

Step-by-step solution

To solve this problem, we will perform the following steps:

  • Step 1: Align the decimal numbers so the decimal points are vertically in line. The numbers are 10.110.1 and 2.32.3.
  • Step 2: Add the numbers starting from the rightmost column (i.e., the tenths place), moving to the left.

Let's perform the addition:

10.1+2.3\begin{array}{c} 10.1 \\ + 2.3 \\ \hline \end{array}

Starting from the right, we add the digits in the tenths place: 1+3=41 + 3 = 4.

Next, add the digits in the units place: 0+2=20 + 2 = 2.

Finally, add the digit in the tens place: 1+0=11 + 0 = 1.

Therefore, the result of adding 10.1+2.310.1 + 2.3 is:

12.412.4

We can verify that this matches with the given answer choices. The correct choice is:

Option 1: 12.412.4

3

Final Answer

12.4

Key Points to Remember

Essential concepts to master this topic
  • Alignment Rule: Line up decimal points vertically before adding numbers
  • Technique: Add column by column: 1+3=4 1 + 3 = 4 in tenths place
  • Check: Count decimal places: both addends have one, answer has one ✓

Common Mistakes

Avoid these frequent errors
  • Adding without aligning decimal points
    Don't just line up the rightmost digits like 10.1+2.3 10.1 + 2.3 becomes 101 + 23 = 124! This ignores place values completely and gives massive errors. Always align the 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 ignore the decimal points and add normally?

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Decimal points show place value! The 1 in 10.1 means 1 tenth, not 1 whole. Ignoring decimals would give you 124 instead of 12.4 - that's off by more than 100!

What if the decimal numbers have different lengths?

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Add trailing zeros to make them the same length! For example, treat 10.1 as 10.10 when adding to 2.30. This makes column addition much clearer.

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

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The decimal point in your answer goes in the same column as the decimal points in the numbers you're adding. It lines up vertically!

Can I add from left to right instead of right to left?

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You can, but it's easier to go right to left in case you need to carry. This matches how we add whole numbers and prevents confusion.

What if I get confused about which column I'm in?

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Label the columns! Write tens | ones | . | tenths above your work. This helps you keep track of place values as you add.

How can I check if my decimal addition is correct?

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Use estimation! Round 10.110 10.1 \approx 10 and 2.32 2.3 \approx 2 , so the answer should be close to 12. Since 12.4 is close to 12, it makes sense!

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