Subtracting Fractions with Unlike Denominators

Oct 13, 2025 by wbrum.org 135 views

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Introduction

Subtracting fractions can be a challenging task, especially when dealing with unlike denominators. However, with a clear understanding of the concept and a step-by-step approach, it becomes manageable. In this article, we will explore the process of subtracting fractions, focusing on the given problem: Subtract $\frac{3}{4} - \frac{3}{10}$ .

Understanding Fractions

Fractions are a way to represent a part of a whole. They consist of two parts: the numerator (the number on top) and the denominator (the number on the bottom). The numerator tells us how many equal parts we have, while the denominator tells us how many parts the whole is divided into.

Example: $\frac{3}{4}$

In this fraction, the numerator is 3, and the denominator is 4. This means we have 3 equal parts out of a total of 4 parts.

Subtracting Fractions with Unlike Denominators

When subtracting fractions with unlike denominators, we need to find a common denominator. The common denominator is the least common multiple (LCM) of the two denominators.

Finding the LCM

To find the LCM of 4 and 10, we need to list the multiples of each number:

Multiples of 4: 4, 8, 12, 16, 20
Multiples of 10: 10, 20, 30, 40, 50

The first number that appears in both lists is 20, which is the LCM of 4 and 10.

Converting Fractions to Have a Common Denominator

Now that we have found the common denominator (20), we need to convert both fractions to have a denominator of 20.

Converting $\frac{3}{4}$

To convert $\frac{3}{4}$ to have a denominator of 20, we need to multiply both the numerator and the denominator by 5:

$\frac{3}{4} \times \frac{5}{5} = \frac{15}{20}$

Converting $\frac{3}{10}$

To convert $\frac{3}{10}$ to have a denominator of 20, we need to multiply both the numerator and the denominator by 2:

$\frac{3}{10} \times \frac{2}{2} = \frac{6}{20}$

Subtracting the Fractions

Now that both fractions have a common denominator (20), we can subtract them:

$\frac{15}{20} - \frac{6}{20} = \frac{9}{20}$

Conclusion

Subtracting fractions with unlike denominators requires finding a common denominator and converting both fractions to have that denominator. By following these steps, we can simplify the subtraction process and arrive at the correct answer. In this case, the answer is $\frac{9}{20}$ .

Frequently Asked Questions

Q: What is the common denominator of 4 and 10?

A: The common denominator of 4 and 10 is 20.

Q: How do I convert a fraction to have a common denominator?

A: To convert a fraction to have a common denominator, multiply both the numerator and the denominator by the necessary factor to achieve the common denominator.

Q: Can I subtract fractions with unlike denominators without finding a common denominator?

A: No, you cannot subtract fractions with unlike denominators without finding a common denominator. This is because the denominators are different, and you need to find a way to make them the same in order to perform the subtraction.

Final Answer

The final answer is $\boxed{\frac{9}{20}}$ .

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Introduction

Q&A: Subtracting Fractions

Q: What is the common denominator of 4 and 10?

A: The common denominator of 4 and 10 is 20.

Q: How do I convert a fraction to have a common denominator?

A: To convert a fraction to have a common denominator, multiply both the numerator and the denominator by the necessary factor to achieve the common denominator.

Q: Can I subtract fractions with unlike denominators without finding a common denominator?

Q: What is the least common multiple (LCM) of 4 and 10?

A: The LCM of 4 and 10 is 20.

Q: How do I find the LCM of two numbers?

A: To find the LCM of two numbers, list the multiples of each number and find the first number that appears in both lists.

Q: Can I subtract fractions with like denominators?

A: Yes, you can subtract fractions with like denominators. In this case, you can simply subtract the numerators and keep the same denominator.

Q: What is the difference between subtracting fractions and subtracting whole numbers?

A: Subtracting fractions involves finding a common denominator and subtracting the numerators, while subtracting whole numbers involves simply subtracting the numbers.

Q: Can I add and subtract fractions with unlike denominators?

A: Yes, you can add and subtract fractions with unlike denominators. However, you need to find a common denominator for both operations.

Q: How do I simplify a fraction after subtracting?

A: To simplify a fraction after subtracting, divide both the numerator and the denominator by their greatest common divisor (GCD).

Q: What is the GCD of 9 and 20?

A: The GCD of 9 and 20 is 1.

Q: Can I simplify a fraction with a denominator of 1?

A: Yes, you can simplify a fraction with a denominator of 1. In this case, the fraction is already in its simplest form.

Conclusion

Final Answer

The final answer is $\boxed{\frac{9}{20}}$ .