Calculate the Sum: 8.5 + 5.2 + 8.4 Addition Problem

Decimal Addition with Mixed Whole Numbers

Solve the following exercise:

8.5+5.2+8.4= ? 8.5+5.2+8.4=\text{ ?}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve
00:03 Let's break down each number into its whole number and decimal point
00:30 We'll use the commutative property to arrange the exercise in a convenient way to solve
00:56 Let's solve one operation at a time separately
01:12 Let's continue solving
01:21 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

Solve the following exercise:

8.5+5.2+8.4= ? 8.5+5.2+8.4=\text{ ?}

2

Step-by-step solution

First we will break down each of the factors in the exercise into a whole number and its remainder:

8+0.5+5+0.2+8+0.4= 8+0.5+5+0.2+8+0.4=

Now we'll combine only the whole numbers:

8+5+8=13+8=21 8+5+8=13+8=21

Then we'll calculate the remainder:

0.5+0.2+0.4=0.7+0.4=1.1 0.5+0.2+0.4=0.7+0.4=1.1

Finally, we are left with the following:

21+1.1=22.1 21+1.1=22.1

3

Final Answer

22.1

Key Points to Remember

Essential concepts to master this topic
  • Alignment: Line up decimal points to keep place values organized
  • Strategy: Separate whole numbers (8+5+8=21) from decimals (0.5+0.2+0.4=1.1)
  • Check: Add vertically: 8.5+5.2+8.4 should equal 22.1 ✓

Common Mistakes

Avoid these frequent errors
  • Adding without aligning decimal points
    Don't add 85+52+84 treating them as whole numbers = 221! This ignores place value completely and gives answers 10 times too large. Always align decimal points vertically before adding.

Practice Quiz

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FAQ

Everything you need to know about this question

Why should I separate whole numbers from decimal parts?

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Separating makes the calculation easier and clearer! Instead of working with mixed decimals, you can add 8+5+8=21 and 0.5+0.2+0.4=1.1 separately, then combine for 22.1.

What if the decimal parts add up to more than 1?

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That's normal! In this problem, 0.5+0.2+0.4=1.1 0.5+0.2+0.4=1.1 . The 1 gets added to your whole number total, and the 0.1 stays as the decimal part.

Can I just line up the numbers without separating them?

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Yes! You can add vertically by aligning decimal points: 8.5 + 5.2 + 8.4. Both methods work, but separating helps you understand place value better.

How do I check if my decimal addition is correct?

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Add the numbers in a different order or use the vertical method if you used separation. For example: 5.2 + 8.4 + 8.5 should still equal 22.1!

What happens if I forget to align the decimal points?

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You'll get a completely wrong answer! For instance, treating 8.5 as 85 would give you 221 instead of 22.1. Always double-check your decimal point placement.

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