Solve: Adding Fractions 4/5 + 1/3 with Unlike Denominators

Fraction Addition with Common Denominator Method

45+13= \frac{4}{5}+\frac{1}{3}=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:03 Let's solve this problem together!
00:06 We need to find the least common denominator. Ready?
00:10 Multiply each fraction by the other's denominator to align them.
00:14 Remember, multiply both the top and bottom numbers, or numerators and denominators.
00:27 Now, let's calculate these multiplications. You're doing great!
00:33 Next, add the fractions using this common denominator.
00:41 It's time to calculate the new top number, or numerator.
00:46 And there you have it! That's how we solve this question.

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

45+13= \frac{4}{5}+\frac{1}{3}=

2

Step-by-step solution

To solve 45+13\frac{4}{5} + \frac{1}{3}, follow these steps:

  • Step 1: Identify a common denominator for the fractions. The current denominators are 55 and 33, hence their common denominator is 1515 (since 5×3=155 \times 3 = 15).
  • Step 2: Convert each fraction to an equivalent fraction with the common denominator 1515:
    • For 45\frac{4}{5}: multiply the numerator and the denominator by 33 (since 5×3=155 \times 3 = 15).
      45=4×35×3=1215\frac{4}{5} = \frac{4 \times 3}{5 \times 3} = \frac{12}{15}.
    • For 13\frac{1}{3}: multiply the numerator and the denominator by 55 (since 3×5=153 \times 5 = 15).
      13=1×53×5=515\frac{1}{3} = \frac{1 \times 5}{3 \times 5} = \frac{5}{15}.
  • Step 3: Add the converted fractions:
    1215+515=12+515=1715\frac{12}{15} + \frac{5}{15} = \frac{12 + 5}{15} = \frac{17}{15}.

Therefore, the solution to the problem is 1715\frac{17}{15}.

3

Final Answer

1715 \frac{17}{15}

Key Points to Remember

Essential concepts to master this topic
  • Rule: Find the LCD before adding fractions with different denominators
  • Technique: Convert 45 \frac{4}{5} to 1215 \frac{12}{15} and 13 \frac{1}{3} to 515 \frac{5}{15}
  • Check: Verify 1215+515=1715 \frac{12}{15} + \frac{5}{15} = \frac{17}{15} by adding numerators ✓

Common Mistakes

Avoid these frequent errors
  • Adding numerators and denominators separately
    Don't add 45+13 \frac{4}{5} + \frac{1}{3} as 4+15+3=58 \frac{4+1}{5+3} = \frac{5}{8} ! This ignores that fractions represent parts of different-sized wholes. Always find a common denominator first, then add only the numerators.

Practice Quiz

Test your knowledge with interactive questions

Complete the following exercise:

\( \frac{3}{4}:\frac{5}{6}=\text{?} \)

FAQ

Everything you need to know about this question

Why can't I just add the numerators and denominators directly?

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Because 45 \frac{4}{5} and 13 \frac{1}{3} represent parts of different-sized wholes! Think of it like adding 4 slices of a 5-slice pizza to 1 slice of a 3-slice pizza - you need equal-sized pieces first.

How do I find the LCD of 5 and 3?

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Since 5 and 3 are both prime numbers, their LCD is simply 5 × 3 = 15. For other numbers, list multiples of each until you find the smallest common one.

Why is my answer bigger than 1?

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That's correct! 1715 \frac{17}{15} equals 1 and 215 \frac{2}{15} , which makes sense since 45 \frac{4}{5} is close to 1 and we're adding more to it.

Should I convert my answer to a mixed number?

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It depends on what the problem asks for! 1715 \frac{17}{15} as an improper fraction is perfectly valid, but you could also write it as 1215 1\frac{2}{15} .

What if the denominators have more than two different numbers?

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The same process works! Find the LCD of all denominators, convert each fraction, then add all the numerators together. The method stays the same no matter how many fractions you have.

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