Compare Fractions: Find the Symbol Between 5/12 and 7/8

Fraction Comparison with Common Denominators

Fill in the missing sign:

51278 \frac{5}{12}☐\frac{7}{8}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:04 Let's begin by choosing the correct sign.
00:08 To compare fractions, we need a common denominator.
00:14 Multiply the left fraction by 2 to find a match.
00:20 Great! This gives us the left fraction with a common denominator.
00:26 Now, let's work on the right fraction.
00:30 Multiply both top and bottom by 3.
00:34 Now, the right fraction also has a common denominator.
00:43 Look closely! The right fraction is larger.
00:50 And that's how we solve this problem!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Fill in the missing sign:

51278 \frac{5}{12}☐\frac{7}{8}

2

Step-by-step solution

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

  • Step 1: Identify the least common multiple (LCM) of the denominators 12 and 8.
  • Step 2: Convert each fraction to have this common denominator.
  • Step 3: Compare the converted fractions by examining their numerators.

Let's proceed with the solution:
Step 1: The LCM of 12 and 8 needs to be found. The factorization of 12 is 22×3 2^2 \times 3 and for 8 is 23 2^3 . The LCM is 23×3=24 2^3 \times 3 = 24 . Therefore, the common denominator is 24.

Step 2: Convert each fraction to the new denominator:

  • Convert 512 \frac{5}{12} : The equivalent fraction is found by multiplying both the numerator and the denominator by a number that equals the common denominator when the original denominator is multiplied by it. 24÷12=2 24 ÷ 12 = 2 . Thus, multiply both the numerator and denominator by 2: 5×212×2=1024 \frac{5 \times 2}{12 \times 2} = \frac{10}{24} .
  • Convert 78 \frac{7}{8} : Similarly, multiply by 24÷8=3 24 ÷ 8 = 3 : 7×38×3=2124 \frac{7 \times 3}{8 \times 3} = \frac{21}{24} .

Step 3: Compare the two equivalent fractions 1024 \frac{10}{24} and 2124 \frac{21}{24} . Comparing the numerators while the denominators are the same: 10 < 21.

Therefore, 512 \frac{5}{12} is less than 78 \frac{7}{8} .

Thus, the correct sign to fill in is < < .

3

Final Answer

< <

Key Points to Remember

Essential concepts to master this topic
  • Rule: Convert fractions to common denominators before comparing numerators
  • Technique: Find LCM of 12 and 8: 23×3=24 2^3 \times 3 = 24
  • Check: Verify 1024<2124 \frac{10}{24} < \frac{21}{24} since 10 < 21 ✓

Common Mistakes

Avoid these frequent errors
  • Comparing fractions without finding common denominators
    Don't compare 5 to 7 and 12 to 8 separately = wrong conclusion! This ignores that different denominators represent different-sized pieces. Always find the LCM and convert both fractions first.

Practice Quiz

Test your knowledge with interactive questions

Fill in the missing sign:

\( \frac{5}{25}☐\frac{1}{5} \)

FAQ

Everything you need to know about this question

Why can't I just compare the numerators 5 and 7?

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Because the denominators are different! 5 twelfths and 7 eighths are completely different sizes. You need a common denominator to make fair comparisons.

How do I find the LCM of 12 and 8 quickly?

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List multiples: 12, 24, 36... and 8, 16, 24, 32... The first number that appears in both lists is 24. Or use prime factorization: 12=22×3 12 = 2^2 \times 3 , 8=23 8 = 2^3 , so LCM = 23×3=24 2^3 \times 3 = 24 .

What if the fractions end up being equal?

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Then you'd use the equals sign (=)! Just convert to common denominators and see if the numerators are the same.

Is there a faster way than finding the LCM?

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You could cross-multiply: 5×8=40 5 \times 8 = 40 and 7×12=84 7 \times 12 = 84 . Since 40 < 84, we get 512<78 \frac{5}{12} < \frac{7}{8} . Both methods work!

Why do we multiply by 2 for the first fraction?

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Because 24÷12=2 24 ÷ 12 = 2 . To get from denominator 12 to 24, we multiply by 2. We must multiply the numerator by the same number to keep the fraction equivalent.

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