Decimal Addition: Solving 0.4 + 0.4

Decimal Addition with Like Place Values

0.4+0.4= 0.4+0.4=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:04 Let's solve this problem together!
00:08 First, we'll use long addition to help us calculate.
00:12 Be sure to place the decimal point correctly, just like lining up numbers.
00:17 We'll start adding from the smallest digits, from right to left.
00:21 Keep adding the numbers step by step.
00:25 And there you have it, the answer to our question!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

0.4+0.4= 0.4+0.4=

2

Step-by-step solution

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

  • Step 1: Align the decimal points vertically in the numbers to be added.
  • Step 2: Add the numbers as if they were whole numbers, placing the decimal correctly in the sum.

Let's perform the addition:

Step 1: Align the numbers 0.4 0.4 and 0.4 0.4 : +0.4+0.4\begin{array}{c} \phantom{+}0.4 \\ + 0.4 \\ \hline \end{array}

Step 2: Add 4 4 and 4 4 in the tenths place, which gives us 8 8 . The decimal point remains in the same position, resulting in 0.8 0.8 .

Therefore, the sum of 0.4+0.4 0.4 + 0.4 is 0.8 0.8 .

3

Final Answer

0.8

Key Points to Remember

Essential concepts to master this topic
  • Alignment Rule: Line up decimal points vertically before adding
  • Technique: Add digits in same place: 4 tenths + 4 tenths = 8 tenths
  • Check: Convert to fractions: 4/10 + 4/10 = 8/10 = 0.8 ✓

Common Mistakes

Avoid these frequent errors
  • Adding digits without considering place value
    Don't just add 4 + 4 = 8 and write 8 anywhere = wrong place value! This ignores that both 4s are in the tenths place, not ones place. Always align decimal points first, then add digits in their correct positions.

Practice Quiz

Test your knowledge with interactive questions

\( \text{0.6+0}.5= \)

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FAQ

Everything you need to know about this question

Why can't I just add 4 + 4 = 8?

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You can add 4 + 4 = 8, but you must remember these are tenths, not whole numbers! So 4 tenths + 4 tenths = 8 tenths, which equals 0.8 0.8 .

What if I forgot to line up the decimal points?

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Always rewrite the problem vertically with decimal points aligned before adding. This prevents place value errors and makes the 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. Keep them all lined up!

Is 0.8 the same as 8 tenths?

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Yes! 0.8 0.8 means 8 tenths. You can think of it as 810 \frac{8}{10} or 8 out of 10 equal parts.

What's the difference between 0.8 and 0.80?

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They're exactly the same value! Adding zeros after the last digit to the right of a decimal point doesn't change the number's value.

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