Solve the Fraction Subtraction: 1/2 - 2/7 Step-by-Step

Fraction Subtraction with Different Denominators

Solve the following exercise:

1227=? \frac{1}{2}-\frac{2}{7}=\text{?}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:05 Let's solve this problem together!
00:09 First, multiply by the second denominator.
00:13 Remember, multiply both the numerator and the denominator by this number.
00:25 Now, let's calculate the products.
00:32 Next, subtract using the common denominator.
00:36 Then, calculate the new numerator.
00:40 And there you have it, 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:

1227=? \frac{1}{2}-\frac{2}{7}=\text{?}

2

Step-by-step solution

To solve the given problem 1227 \frac{1}{2} - \frac{2}{7} , we need to follow these steps:

  • Step 1: Find a common denominator for the fractions. The denominators are 2 and 7. The common denominator can be found by multiplying these two numbers: 2×7=14 2 \times 7 = 14 .
  • Step 2: Convert the fractions to equivalent fractions with the common denominator. For 12 \frac{1}{2} , multiply the numerator and the denominator by 7: 12=1×72×7=714 \frac{1}{2} = \frac{1 \times 7}{2 \times 7} = \frac{7}{14} . For 27 \frac{2}{7} , multiply the numerator and the denominator by 2: 27=2×27×2=414 \frac{2}{7} = \frac{2 \times 2}{7 \times 2} = \frac{4}{14} .
  • Step 3: Subtract the fractions. With a common denominator, subtract the numerators: 714414=7414=314 \frac{7}{14} - \frac{4}{14} = \frac{7 - 4}{14} = \frac{3}{14} .
  • Step 4: Simplify the resulting fraction if needed. The fraction 314\frac{3}{14} is already in its simplest form.

Thus, the solution to the problem is 314 \frac{3}{14} .

3

Final Answer

314 \frac{3}{14}

Key Points to Remember

Essential concepts to master this topic
  • Common Denominator: Find LCD by multiplying denominators when they're coprime
  • Technique: Convert 12 \frac{1}{2} to 714 \frac{7}{14} and 27 \frac{2}{7} to 414 \frac{4}{14}
  • Check: Verify 714414=314 \frac{7}{14} - \frac{4}{14} = \frac{3}{14} cannot be simplified further ✓

Common Mistakes

Avoid these frequent errors
  • Subtracting denominators along with numerators
    Don't subtract 1227 \frac{1}{2} - \frac{2}{7} as 1227=15 \frac{1-2}{2-7} = \frac{-1}{-5} ! You can only add or subtract numerators when denominators are the same. 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 division! 12 \frac{1}{2} means 1÷2, not just "1 and 2". You need the same denominator to combine fractions, just like you need the same units to add measurements.

How do I find the common denominator when the numbers don't divide evenly?

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When denominators like 2 and 7 have no common factors, multiply them together: 2×7=14. This gives you the least common denominator quickly!

Do I always multiply the denominators to get the LCD?

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Not always! If one denominator divides the other (like 4 and 12), use the larger number as your LCD. Only multiply when they share no common factors.

How do I know if my final fraction can be simplified?

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Check if the numerator and denominator share any common factors. For 314 \frac{3}{14} , since 3 and 14 share no common factors, it's already simplified!

What if I get a negative answer?

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That's normal! If the first fraction is smaller than the second, your answer will be negative. Just follow the same steps and keep the negative sign with your final answer.

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