Solve the Fraction Subtraction: 3/4 - 3/9 Step by Step

Fraction Subtraction with Different Denominators

Solve the following exercise:

3439=? \frac{3}{4}-\frac{3}{9}=\text{?}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve
00:03 Multiply by the second denominator to find the common denominator
00:07 Make sure to multiply both numerator and denominator
00:18 Calculate the multiplications
00:30 Subtract with the common denominator
00:33 Calculate the numerator
00:38 Reduce the fraction as much as possible
00:42 Make sure to divide both numerator and denominator
00:48 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:

3439=? \frac{3}{4}-\frac{3}{9}=\text{?}

2

Step-by-step solution

To solve this problem, we'll follow these steps:

  • Step 1: Find a common denominator for the fractions 34 \frac{3}{4} and 39 \frac{3}{9} .
  • Step 2: Convert each fraction to have this common denominator.
  • Step 3: Subtract the numerators while keeping the common denominator.
  • Step 4: Simplify the resultant fraction if possible.

Now, let's work through each step:

Step 1: The denominators of the fractions are 4 and 9. The least common multiple of 4 and 9 is 36. Therefore, 36 will be our common denominator.

Step 2: Convert 34 \frac{3}{4} and 39 \frac{3}{9} to have a denominator of 36:

34×99=2736 \frac{3}{4} \times \frac{9}{9} = \frac{27}{36} and 39×44=1236 \frac{3}{9} \times \frac{4}{4} = \frac{12}{36}

Step 3: Now, subtract the fractions:

27361236=1536 \frac{27}{36} - \frac{12}{36} = \frac{15}{36}

Step 4: Simplify 1536 \frac{15}{36} :

Both 15 and 36 can be divided by their greatest common divisor, which is 3. Dividing both the numerator and denominator by 3, we get:

15÷336÷3=512 \frac{15 \div 3}{36 \div 3} = \frac{5}{12}

Therefore, the solution to the problem is 512 \frac{5}{12} .

3

Final Answer

512 \frac{5}{12}

Key Points to Remember

Essential concepts to master this topic
  • Rule: Find the least common multiple of denominators first
  • Technique: Convert 34 \frac{3}{4} to 2736 \frac{27}{36} by multiplying by 99 \frac{9}{9}
  • Check: Verify 27361236=1536=512 \frac{27}{36} - \frac{12}{36} = \frac{15}{36} = \frac{5}{12}

Common Mistakes

Avoid these frequent errors
  • Subtracting numerators and denominators separately
    Don't subtract 3439 \frac{3}{4} - \frac{3}{9} as 3349=05 \frac{3-3}{4-9} = \frac{0}{-5} ! This completely ignores fraction rules and gives meaningless results. 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 3-3 and 4-9?

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Fractions don't work like regular subtraction! You can only subtract numerators when the denominators are the same. Think of it like pizza slices - you can't subtract quarters from ninths directly.

How do I find the least common multiple of 4 and 9?

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List multiples: 4, 8, 12, 16, 20, 24, 28, 32, 36 and 9, 18, 27, 36. The first number that appears in both lists is your LCM!

Do I always need to simplify my final answer?

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Yes! Always check if your answer can be reduced. Divide both numerator and denominator by their greatest common factor. 1536 \frac{15}{36} becomes 512 \frac{5}{12} when divided by 3.

What if the denominators are already the same?

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Lucky you! Just subtract the numerators and keep the same denominator. For example: 710310=410=25 \frac{7}{10} - \frac{3}{10} = \frac{4}{10} = \frac{2}{5} .

Can the answer be larger than the fractions I started with?

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No! In subtraction, your answer will always be smaller than the first fraction. If you get a larger result, check your work - you likely made an error in finding the common denominator.

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