Solve the Fraction Subtraction: 3/5 minus 1/4

Fraction Subtraction with Different Denominators

Solve the following exercise:

3514=? \frac{3}{5}-\frac{1}{4}=\text{?}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:06 Let's solve this step by step.
00:10 First, we need to multiply by the second denominator.
00:14 Remember to multiply both the numerator and the denominator.
00:26 Next, calculate the products of these numbers.
00:33 Now subtract using the common denominator.
00:38 Let's calculate the new numerator.
00:41 And this is how we find 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:

3514=? \frac{3}{5}-\frac{1}{4}=\text{?}

2

Step-by-step solution

To solve the problem of subtracting 14 \frac{1}{4} from 35 \frac{3}{5} , we need a common denominator.

First, find the least common denominator (LCD) of 5 and 4, which is 20. This is done by multiplying the denominators: 5×4=20 5 \times 4 = 20 .

Next, convert each fraction to an equivalent fraction with the denominator of 20:

  • For 35 \frac{3}{5} : Multiply both numerator and denominator by 4 to get 3×45×4=1220 \frac{3 \times 4}{5 \times 4} = \frac{12}{20} .
  • For 14 \frac{1}{4} : Multiply both numerator and denominator by 5 to get 1×54×5=520 \frac{1 \times 5}{4 \times 5} = \frac{5}{20} .

Now perform the subtraction with these equivalent fractions:

1220520=12520=720 \frac{12}{20} - \frac{5}{20} = \frac{12 - 5}{20} = \frac{7}{20}

The resulting fraction, 720 \frac{7}{20} , is already in its simplest form.

Therefore, the solution to the subtraction 3514 \frac{3}{5} - \frac{1}{4} is 720 \frac{7}{20} .

Checking against the multiple-choice answers, the correct choice is the first one: 720 \frac{7}{20} .

3

Final Answer

720 \frac{7}{20}

Key Points to Remember

Essential concepts to master this topic
  • Common Denominator Rule: Find LCD before subtracting fractions with different denominators
  • Conversion Technique: 35=1220 \frac{3}{5} = \frac{12}{20} and 14=520 \frac{1}{4} = \frac{5}{20} when LCD is 20
  • Verification Check: Ensure answer is in simplest form and denominators match during subtraction ✓

Common Mistakes

Avoid these frequent errors
  • Subtracting numerators and denominators separately
    Don't subtract 3514 \frac{3}{5} - \frac{1}{4} as 3154=21 \frac{3-1}{5-4} = \frac{2}{1} ! This completely ignores fraction rules and gives a nonsensical result. Always find the common denominator first, then subtract only the numerators.

Practice Quiz

Test your knowledge with interactive questions

Solve the following:

\( \frac{5}{9}:\frac{7}{18}= \)

FAQ

Everything you need to know about this question

How do I find the LCD of 5 and 4?

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Since 5 and 4 share no common factors (they're relatively prime), their LCD is simply 5 × 4 = 20. For other fractions, you might need to find the actual least common multiple.

Why can't I just subtract the numerators and denominators?

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Fractions represent parts of a whole. You can only combine parts when they're the same size! Think of it like trying to subtract 3 slices of a 5-piece pizza from 1 slice of a 4-piece pizza - you need equal-sized pieces first.

What if my LCD calculation gives me a huge number?

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That's okay! Large denominators are normal when working with fractions. Just be careful with your arithmetic. You can always simplify at the end if the numerator and denominator share common factors.

How do I know when my fraction answer is in simplest form?

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Check if the numerator and denominator share any common factors. For 720 \frac{7}{20} , since 7 is prime and doesn't divide 20, it's already simplified!

Can I convert to decimals instead of finding LCD?

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While possible, it's often messier! 35=0.6 \frac{3}{5} = 0.6 and 14=0.25 \frac{1}{4} = 0.25 gives 0.35, but converting back to 720 \frac{7}{20} requires extra steps. LCD method is usually cleaner!

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