Solve Mixed Number Addition: 3½ + 5⅘ Step by Step

Mixed Number Addition with Different Denominators

312+545= 3\frac{1}{2}+5\frac{4}{5}=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve
00:03 First convert mixed numbers to fractions
00:47 Multiply each fraction by the second denominator to find the common denominator
01:01 Calculate the multiplications
01:15 Add with the common denominator
01:25 Now convert to mixed number
01:30 Break down 93 into 90 plus 3
01:38 Break down the fraction into whole number and remainder
01:43 Convert whole number to integer, and combine with mixed fraction
01:52 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

312+545= 3\frac{1}{2}+5\frac{4}{5}=

2

Step-by-step solution

To solve the problem of adding 312 3\frac{1}{2} and 545 5\frac{4}{5} , we will proceed as follows:

Step 1: Add the whole numbers.
The whole numbers are 3 3 and 5 5 . Thus, 3+5=8 3 + 5 = 8 .

Step 2: Add the fractional parts.
The fractions are 12\frac{1}{2} and 45\frac{4}{5}. To add these, we need a common denominator:

  • The denominators are 22 and 55. The least common denominator (LCD) is 1010.
  • Convert 12\frac{1}{2} to an equivalent fraction with a denominator of 1010:
  • 12=1×52×5=510 \frac{1}{2} = \frac{1 \times 5}{2 \times 5} = \frac{5}{10}
  • Convert 45\frac{4}{5} to an equivalent fraction with a denominator of 1010:
  • 45=4×25×2=810 \frac{4}{5} = \frac{4 \times 2}{5 \times 2} = \frac{8}{10}
  • Add these fractions:
  • 510+810=1310 \frac{5}{10} + \frac{8}{10} = \frac{13}{10}

Step 3: Convert the improper fraction 1310\frac{13}{10} to a mixed number:
1310=1310\frac{13}{10} = 1\frac{3}{10}.

Step 4: Add the result from step 1 (the sum of whole numbers) to the mixed fraction obtained in step 3:
8+1310=93108 + 1\frac{3}{10} = 9\frac{3}{10}.

Therefore, the sum of 312+545 3\frac{1}{2} + 5\frac{4}{5} is 9310 9\frac{3}{10} .

3

Final Answer

9310 9\frac{3}{10}

Key Points to Remember

Essential concepts to master this topic
  • Rule: Find common denominator before adding fractional parts
  • Technique: Convert 12 \frac{1}{2} to 510 \frac{5}{10} and 45 \frac{4}{5} to 810 \frac{8}{10} using LCD 10
  • Check: Convert improper fraction 1310 \frac{13}{10} to mixed number 1310 1\frac{3}{10} , then add to whole number sum ✓

Common Mistakes

Avoid these frequent errors
  • Adding whole numbers and fractions separately without proper conversion
    Don't just add 3+5=8 and 12+45 \frac{1}{2}+\frac{4}{5} without finding common denominators = wrong answer like 857 8\frac{5}{7} ! You can't add fractions with different denominators directly. Always find the LCD first, then convert both fractions before adding.

Practice Quiz

Test your knowledge with interactive questions

\( 5:\frac{2}{5}= \)

FAQ

Everything you need to know about this question

Why can't I just add 1/2 + 4/5 directly?

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You can't add fractions with different denominators directly because they represent different-sized pieces. It's like trying to add apples and oranges! You need a common denominator first.

How do I find the least common denominator of 2 and 5?

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Since 2 and 5 are both prime numbers, their LCD is their product: 2 × 5 = 10. For other numbers, list multiples of each until you find the smallest one they share.

What do I do when I get an improper fraction like 13/10?

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Convert it to a mixed number! 1310=1310 \frac{13}{10} = 1\frac{3}{10} because 13 ÷ 10 = 1 remainder 3. Then add this extra whole number to your sum from step 1.

Can I convert to decimals instead of finding common denominators?

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Yes! 312=3.5 3\frac{1}{2} = 3.5 and 545=5.8 5\frac{4}{5} = 5.8 , so 3.5 + 5.8 = 9.3 = 9310 9\frac{3}{10} . Both methods work perfectly!

Why is my answer different from the multiple choice options?

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Double-check your common denominator work! The most common error is using the wrong LCD or making arithmetic mistakes when converting fractions. Always verify by converting your answer to decimals.

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