Adding Fractions: Solve 1/4 + 7/8 Step by Step

Fraction Addition with Different Denominators

14+78= \frac{1}{4}+\frac{7}{8}=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solution
00:03 We want to find the least common denominator
00:06 Multiply by 2 to find the common denominator
00:09 Remember to multiply both numerator and denominator
00:17 Calculate the products
00:22 Add under the common denominator
00:28 Calculate the numerator
00:31 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

14+78= \frac{1}{4}+\frac{7}{8}=

2

Step-by-step solution

To find the sum 14+78 \frac{1}{4} + \frac{7}{8} , follow these steps:

  • Step 1: Identify the least common denominator (LCD) of the fractions. The denominators 4 and 8 have an LCD of 8.
  • Step 2: Convert 14 \frac{1}{4} to an equivalent fraction with a denominator of 8. Multiply both the numerator and the denominator by 2: 14=1×24×2=28 \frac{1}{4} = \frac{1 \times 2}{4 \times 2} = \frac{2}{8} .
  • Step 3: The second fraction, 78 \frac{7}{8} , already has the correct denominator. Therefore, it remains 78 \frac{7}{8} .
  • Step 4: Add the numerators of the two fractions: 28+78=2+78=98 \frac{2}{8} + \frac{7}{8} = \frac{2+7}{8} = \frac{9}{8} .

Therefore, the sum of 14 \frac{1}{4} and 78 \frac{7}{8} is 98 \frac{9}{8} .

3

Final Answer

98 \frac{9}{8}

Key Points to Remember

Essential concepts to master this topic
  • Rule: Find the least common denominator (LCD) before adding fractions
  • Technique: Convert 14 \frac{1}{4} to 28 \frac{2}{8} by multiplying by 2/2
  • Check: Verify 28+78=98 \frac{2}{8} + \frac{7}{8} = \frac{9}{8} equals 1.125 ✓

Common Mistakes

Avoid these frequent errors
  • Adding numerators and denominators separately
    Don't add 1+7=8 and 4+8=12 to get 812 \frac{8}{12} ! This creates a completely wrong fraction because you're not following proper fraction addition rules. Always find the LCD first, convert fractions to equivalent forms, 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 1+7 and 4+8 directly?

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Because fractions represent parts of a whole, and you can only add parts that are the same size! 14 \frac{1}{4} means 1 piece out of 4, while 78 \frac{7}{8} means 7 pieces out of 8. These are different-sized pieces, so you need to make them the same size first.

How do I find the LCD of 4 and 8?

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List the multiples: 4: (4, 8, 12, 16...) and 8: (8, 16, 24...). The smallest number that appears in both lists is 8, so LCD = 8.

What if my answer is an improper fraction like 9/8?

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That's perfectly correct! 98 \frac{9}{8} is a valid answer. You can also write it as a mixed number: 118 1\frac{1}{8} , but the improper fraction form is fine too.

Do I always need to find the LCD?

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Yes, when denominators are different! If one denominator divides evenly into the other (like 4 and 8), the larger one is your LCD. This makes converting fractions much easier.

How can I check if my answer is right?

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Convert both fractions to decimals: 14=0.25 \frac{1}{4} = 0.25 and 78=0.875 \frac{7}{8} = 0.875 . Add them: 0.25 + 0.875 = 1.125. Then check: 98=1.125 \frac{9}{8} = 1.125

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