Solve the Fraction Subtraction: 7/8 minus 5/12

Fraction Subtraction with Different Denominators

Solve the following exercise:

78512=? \frac{7}{8}-\frac{5}{12}=\text{?}

❤️ Continue Your Math Journey!

We have hundreds of course questions with personalized recommendations + Account 100% premium

Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve
00:03 We want to find the least common denominator
00:06 Multiply by 3 and 2 respectively to find the common denominator
00:09 Make sure to multiply both numerator and denominator
00:21 Calculate the multiplications
00:29 Subtract with the common denominator
00:36 Calculate the numerator
00:40 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:

78512=? \frac{7}{8}-\frac{5}{12}=\text{?}

2

Step-by-step solution

To solve the problem of subtracting 512\frac{5}{12} from 78\frac{7}{8}, we follow these steps:

  • Step 1: Find the least common multiple (LCM) of the denominators 8 and 12. The multiples of 8 are 8, 16, 24, 32, and those of 12 are 12, 24, 36. The smallest common multiple is 24.
  • Step 2: Convert each fraction to have a denominator of 24.
    For 78\frac{7}{8}:
    Multiply the numerator and the denominator by 3 to get: 7×38×3=2124\frac{7 \times 3}{8 \times 3} = \frac{21}{24}.
    For 512\frac{5}{12}:
    Multiply the numerator and the denominator by 2 to get: 5×212×2=1024\frac{5 \times 2}{12 \times 2} = \frac{10}{24}.
  • Step 3: Subtract the fractions now that they have the same denominator:
    21241024=211024=1124\frac{21}{24} - \frac{10}{24} = \frac{21 - 10}{24} = \frac{11}{24}.
  • Step 4: Simplify the fraction if possible. In this case, 1124\frac{11}{24} is already in its simplest form.

Therefore, the result of 78512\frac{7}{8} - \frac{5}{12} is 1124\frac{11}{24}.

3

Final Answer

1124 \frac{11}{24}

Key Points to Remember

Essential concepts to master this topic
  • Common Denominator Rule: Find LCD before subtracting unlike fractions
  • Convert Technique: 78=2124 \frac{7}{8} = \frac{21}{24} by multiplying by 3/3
  • Verification Check: 21241024=1124 \frac{21}{24} - \frac{10}{24} = \frac{11}{24}

Common Mistakes

Avoid these frequent errors
  • Subtracting numerators and denominators separately
    Don't subtract straight across like 7-5=2 and 8-12=-4 to get 24 \frac{2}{-4} ! This completely ignores that fractions represent parts of different wholes. Always find the common denominator first, then subtract only the numerators.

Practice Quiz

Test your knowledge with interactive questions

Solve the following exercise:

\( \frac{3}{2}-\frac{1}{2}=\text{?} \)

FAQ

Everything you need to know about this question

Why can't I just subtract the top numbers and bottom numbers separately?

+

Because 78 \frac{7}{8} means 7 out of 8 equal pieces, while 512 \frac{5}{12} means 5 out of 12 equal pieces. You can't subtract different-sized pieces directly! You need to convert both to the same size pieces first.

How do I find the LCD of 8 and 12?

+

List the multiples of each number:

  • 8: 8, 16, 24, 32...
  • 12: 12, 24, 36...
The smallest number that appears in both lists is 24, so that's your LCD!

What if I get a different common denominator like 96?

+

Any common multiple will work, but using the LCD makes your numbers smaller and easier to work with. Using 96 would give you 84964096=4496 \frac{84}{96} - \frac{40}{96} = \frac{44}{96} , which simplifies to the same answer but with more work!

Do I always need to simplify my final answer?

+

Yes! Always check if your answer can be simplified by finding common factors. In this case, 11 and 24 share no common factors (11 is prime), so 1124 \frac{11}{24} is already in lowest terms.

What if the first fraction is smaller than the second?

+

No problem! You'll get a negative answer. For example, 51278=10242124=1124 \frac{5}{12} - \frac{7}{8} = \frac{10}{24} - \frac{21}{24} = -\frac{11}{24} . Just follow the same steps!

🌟 Unlock Your Math Potential

Get unlimited access to all 18 Operations with Fractions questions, detailed video solutions, and personalized progress tracking.

📹

Unlimited Video Solutions

Step-by-step explanations for every problem

📊

Progress Analytics

Track your mastery across all topics

🚫

Ad-Free Learning

Focus on math without distractions

No credit card required • Cancel anytime

More Questions

Click on any question to see the complete solution with step-by-step explanations