Solve Decimal Addition: 20.2 + 8.8

Decimal Addition with Carrying

20.2+8.8= \text{20}.2+8.8=

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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
00:09 Place the decimal point in the appropriate position
00:12 Let's start by adding the smallest appropriate digits
00:19 Place the units and remember 1 above
00:27 Add 1 to this calculation, and place
00:36 Place 0 in the missing digits, calculate and place accordingly
00:44 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

20.2+8.8= \text{20}.2+8.8=

2

Step-by-step solution

To solve this problem, we will add the decimal numbers 20.2 and 8.8. Here is how we proceed:

  • Step 1: Align the decimal numbers:

  • 120.2 \phantom{1}20.2
    ++ 18.8 \phantom{1}8.8
    99.99\overline{\phantom{99.99}}

  • Step 2: Add column by column, starting from the right.

    • First, add the tenths: 2+8=102 + 8 = 10. Since 10 is more than 9, write 0 and carry over 1 to the units column.

    • Then, add the units: 0+8=80 + 8 = 8, plus the carry-over 1 makes it 9.

    • Finally, add the tens: 20+0=2020 + 0 = 20.

  • When combining the results, we get:

    2929.

    Therefore, the sum of 20.220.2 and 8.88.8 is \( \textbf{2929} \).

3

Final Answer

29

Key Points to Remember

Essential concepts to master this topic
  • Rule: Always align decimal points before adding columns vertically
  • Technique: In tenths column: 2 + 8 = 10, write 0 carry 1
  • Check: Verify 20 + 9 = 29 by adding whole numbers separately ✓

Common Mistakes

Avoid these frequent errors
  • Forgetting to carry when adding decimal columns
    Don't just write 10 in the tenths place when 2 + 8 = 10! This gives you 20.10 + 8.8 = 28.18 instead of 29. Always carry the 1 to the next column when any sum equals 10 or more.

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FAQ

Everything you need to know about this question

Why does my answer have more decimal places than the original numbers?

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When adding decimals, you might think you need extra decimal places, but that's not always true! In this problem, 20.2+8.8=29.0 20.2 + 8.8 = 29.0 , which equals 29 exactly.

Do I need to write 29.0 or just 29?

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Both 29.0 and 29 are mathematically correct! However, 29 is the simplest form since the decimal part is zero.

What happens when I add the tenths column and get 10?

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When any column adds up to 10 or more, write down the ones digit and carry the tens digit to the next column left. So 2 + 8 = 10 becomes: write 0, carry 1.

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 position as the decimal points in the numbers you're adding. Since both numbers have one decimal place, align everything vertically.

Can I add decimals without lining them up?

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No! Always line up the decimal points first. Adding 20.2 + 8.8 without alignment leads to mistakes. Proper alignment ensures you're adding tenths to tenths, units to units, etc.

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