Solve the Fraction Subtraction: 4/5 minus 1/3

Fraction Subtraction with Common Denominators

Solve the following exercise:

4513=? \frac{4}{5}-\frac{1}{3}=\text{?}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:07 Alright, let's solve this math problem together.
00:10 First, multiply by the second denominator to find a common one.
00:16 Remember, multiply both the top, or numerator, and the bottom, or denominator.
00:24 Now, let's calculate these multiplications step by step.
00:34 Next, we subtract using this common denominator.
00:40 Let's compute the new numerator now.
00:45 And there we have it! We've found the solution to our question.

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Solve the following exercise:

4513=? \frac{4}{5}-\frac{1}{3}=\text{?}

2

Step-by-step solution

To solve the subtraction of these two fractions, we'll follow these steps:

  • Step 1: Find a common denominator for the fractions 45 \frac{4}{5} and 13 \frac{1}{3} . The denominators are 5 and 3, and multiplying them gives us a common denominator of 15.
  • Step 2: Convert each fraction to have this common denominator:
    • Convert 45 \frac{4}{5} to an equivalent fraction with a denominator of 15. To do this, multiply both the numerator and the denominator by 3: 45=4×35×3=1215\frac{4}{5} = \frac{4 \times 3}{5 \times 3} = \frac{12}{15}.
    • Convert 13 \frac{1}{3} to an equivalent fraction with a denominator of 15. To do this, multiply both the numerator and the denominator by 5: 13=1×53×5=515\frac{1}{3} = \frac{1 \times 5}{3 \times 5} = \frac{5}{15}.
  • Step 3: Perform the subtraction of the numerators, now having the same denominator: 1215515=12515=715\frac{12}{15} - \frac{5}{15} = \frac{12 - 5}{15} = \frac{7}{15}.
  • Step 4: Simplify the result, if possible. In this case, 715\frac{7}{15} is already in its simplest form as 7 and 15 have no common factors other than 1.

Therefore, the solution to the problem is 715\frac{7}{15}.

3

Final Answer

715 \frac{7}{15}

Key Points to Remember

Essential concepts to master this topic
  • Rule: Find common denominator before subtracting fraction numerators
  • Technique: Convert 45 \frac{4}{5} to 1215 \frac{12}{15} and 13 \frac{1}{3} to 515 \frac{5}{15}
  • Check: Verify 715 \frac{7}{15} cannot be simplified further since 7 and 15 share no factors ✓

Common Mistakes

Avoid these frequent errors
  • Subtracting denominators instead of finding common denominator
    Don't subtract 4513=32 \frac{4}{5} - \frac{1}{3} = \frac{3}{2} by doing 4-1=3 and 5-3=2! This completely ignores fraction rules and gives nonsense answers. Always find a common denominator first, then subtract only the numerators.

Practice Quiz

Test your knowledge with interactive questions

\( \frac{1}{3}+\frac{1}{4}= \)

FAQ

Everything you need to know about this question

Why can't I just subtract the numerators and denominators separately?

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Fractions represent parts of a whole! 45 \frac{4}{5} means 4 parts out of 5, while 13 \frac{1}{3} means 1 part out of 3. You can't subtract different-sized parts directly - you need same-sized pieces first!

How do I find the common denominator for 5 and 3?

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Since 5 and 3 are both prime numbers with no common factors, multiply them together: 5 × 3 = 15. This gives you the least common multiple, which becomes your common denominator.

Do I always multiply the denominators together?

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Not always! Only when the denominators share no common factors. For example, with denominators 4 and 6, the LCD is 12 (not 24) because 4 and 6 both divide evenly into 12.

What if my answer can be simplified?

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Always check if you can reduce your fraction! Look for common factors in the numerator and denominator. In this case, 715 \frac{7}{15} cannot be simplified since 7 and 15 share no common factors.

Is there a shortcut for fraction subtraction?

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The cross-multiplication method works too! For abcd \frac{a}{b} - \frac{c}{d} , use adbcbd \frac{ad - bc}{bd} . So 4×31×55×3=12515=715 \frac{4×3 - 1×5}{5×3} = \frac{12-5}{15} = \frac{7}{15} .

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