Finding the GCD of 18 and 15

Oct 13, 2025 by wbrum.org 35 views

Introduction

In mathematics, fractions are a way to represent a part of a whole. They are written in the form of a ratio of two numbers, where the top number is called the numerator and the bottom number is called the denominator. When we have a fraction, we can simplify it by rewriting it in its lowest terms. This means that we need to find the greatest common divisor (GCD) of the numerator and the denominator and divide both numbers by it. In this article, we will learn how to rewrite the fraction $$\frac{18}{15}$$ in its lowest terms.

What is the Greatest Common Divisor (GCD)?

The greatest common divisor (GCD) of two numbers is the largest number that divides both numbers without leaving a remainder. For example, the GCD of 12 and 18 is 6, because 6 is the largest number that divides both 12 and 18 without leaving a remainder.

Finding the GCD of 18 and 15

To find the GCD of 18 and 15, we need to list all the factors of each number and find the largest common factor.

Factors of 18:

Factors of 15:

As we can see, the largest common factor of 18 and 15 is 3. Therefore, the GCD of 18 and 15 is 3.

Rewriting the Fraction in Lowest Terms

Now that we have found the GCD of 18 and 15, we can rewrite the fraction $$\frac{18}{15}$$ in its lowest terms by dividing both numbers by the GCD.

\frac{18}{15} = \frac{18 \div 3}{15 \div 3} = \frac{6}{5}

Therefore, the fraction $$\frac{18}{15}$$ can be rewritten in its lowest terms as $$\frac{6}{5}$$.

Why is it Important to Rewrite Fractions in Lowest Terms?

Rewriting fractions in lowest terms is important because it makes it easier to compare and add fractions. When fractions are in their lowest terms, we can easily compare their values and add them together.

Example: Comparing Fractions

Suppose we have two fractions: $$\frac{1}{2}$$ and $$\frac{2}{4}$$. To compare these fractions, we need to rewrite them in their lowest terms.

\frac{1}{2} = \frac{1}{2}$$ (already in lowest terms)

\frac{2}{4} = \frac{2 \div 2}{4 \div 2} = \frac{1}{2} </span></p> <p>As we can see, both fractions are equal to $$\frac{1}{2}$$. Therefore, we can conclude that $$\frac{1}{2}$$ is greater than $$\frac{2}{4}$$.</p> <h2><strong>Conclusion</strong></h2> <p>In conclusion, rewriting fractions in lowest terms is an important concept in mathematics. It makes it easier to compare and add fractions. In this article, we learned how to rewrite the fraction $$\frac{18}{15}$$ in its lowest terms by finding the GCD of the numerator and the denominator and dividing both numbers by it. We also learned why it is important to rewrite fractions in lowest terms and how to compare fractions.</p> <h2><strong>Frequently Asked Questions</strong></h2> <h3>Q: What is the greatest common divisor (GCD) of two numbers?</h3> <p>A: The greatest common divisor (GCD) of two numbers is the largest number that divides both numbers without leaving a remainder.</p> <h3>Q: How do I find the GCD of two numbers?</h3> <p>A: To find the GCD of two numbers, you need to list all the factors of each number and find the largest common factor.</p> <h3>Q: Why is it important to rewrite fractions in lowest terms?</h3> <p>A: Rewriting fractions in lowest terms is important because it makes it easier to compare and add fractions.</p> <h3>Q: How do I compare fractions?</h3> <p>A: To compare fractions, you need to rewrite them in their lowest terms and then compare their values.</p> <h2><strong>References</strong></h2> <ul> <li>[1] Khan Academy. (n.d.). Greatest Common Divisor (GCD). Retrieved from <a href="https://www.khanacademy.org/math/pre-algebra/pre-algebra-fractions/pre-algebra-gcd">https://www.khanacademy.org/math/pre-algebra/pre-algebra-fractions/pre-algebra-gcd</a></li> <li>[2] Math Open Reference. (n.d.). Greatest Common Divisor (GCD). Retrieved from <a href="https://www.mathopenref.com/gcd.html">https://www.mathopenref.com/gcd.html</a></li> </ul> <h2><strong>Glossary</strong></h2> <ul> <li><strong>Greatest Common Divisor (GCD):</strong> The largest number that divides both numbers without leaving a remainder.</li> <li><strong>Numerator:</strong> The top number in a fraction.</li> <li><strong>Denominator:</strong> The bottom number in a fraction.</li> <li><strong>Fraction:</strong> A way to represent a part of a whole.</li> <li><strong>Lowest Terms:</strong> A fraction that has been simplified by dividing both numbers by their greatest common divisor.<br/> <strong>Frequently Asked Questions: Fractions and Greatest Common Divisor (GCD)</strong> ====================================================================</li> </ul> <h2><strong>Q: What is the greatest common divisor (GCD) of two numbers?</strong></h2> <p>A: The greatest common divisor (GCD) of two numbers is the largest number that divides both numbers without leaving a remainder.</p> <h2><strong>Q: How do I find the GCD of two numbers?</strong></h2> <p>A: To find the GCD of two numbers, you need to list all the factors of each number and find the largest common factor.</p> <h2><strong>Q: What is the difference between the GCD and the least common multiple (LCM)?</strong></h2> <p>A: The greatest common divisor (GCD) is the largest number that divides both numbers without leaving a remainder, while the least common multiple (LCM) is the smallest number that is a multiple of both numbers.</p> <h2><strong>Q: How do I simplify a fraction?</strong></h2> <p>A: To simplify a fraction, you need to find the greatest common divisor (GCD) of the numerator and the denominator and divide both numbers by it.</p> <h2><strong>Q: What is the purpose of rewriting fractions in lowest terms?</strong></h2> <p>A: Rewriting fractions in lowest terms is important because it makes it easier to compare and add fractions.</p> <h2><strong>Q: How do I compare fractions?</strong></h2> <p>A: To compare fractions, you need to rewrite them in their lowest terms and then compare their values.</p> <h2><strong>Q: What is the difference between equivalent fractions and equivalent ratios?</strong></h2> <p>A: Equivalent fractions are fractions that have the same value, while equivalent ratios are ratios that have the same value.</p> <h2><strong>Q: How do I convert a mixed number to an improper fraction?</strong></h2> <p>A: To convert a mixed number to an improper fraction, you need to multiply the whole number by the denominator and add the numerator, then write the result as an improper fraction.</p> <h2><strong>Q: What is the difference between a proper fraction and an improper fraction?</strong></h2> <p>A: A proper fraction is a fraction where the numerator is less than the denominator, while an improper fraction is a fraction where the numerator is greater than or equal to the denominator.</p> <h2><strong>Q: How do I add and subtract fractions?</strong></h2> <p>A: To add and subtract fractions, you need to have the same denominator, then add or subtract the numerators and keep the same denominator.</p> <h2><strong>Q: What is the difference between adding and subtracting fractions with like denominators and unlike denominators?</strong></h2> <p>A: Adding and subtracting fractions with like denominators is easier because you can simply add or subtract the numerators, while adding and subtracting fractions with unlike denominators requires finding the least common multiple (LCM) of the denominators.</p> <h2><strong>Q: How do I multiply and divide fractions?</strong></h2> <p>A: To multiply fractions, you need to multiply the numerators and multiply the denominators, then simplify the result. To divide fractions, you need to invert the second fraction and multiply.</p> <h2><strong>Q: What is the difference between multiplying and dividing fractions with like denominators and unlike denominators?</strong></h2> <p>A: Multiplying and dividing fractions with like denominators is easier because you can simply multiply or divide the numerators and denominators, while multiplying and dividing fractions with unlike denominators requires finding the least common multiple (LCM) of the denominators.</p> <h2><strong>Q: How do I solve problems involving fractions and mixed numbers?</strong></h2> <p>A: To solve problems involving fractions and mixed numbers, you need to convert the mixed number to an improper fraction, then perform the operations as usual.</p> <h2><strong>Q: What is the difference between solving problems involving fractions and mixed numbers and solving problems involving only fractions?</strong></h2> <p>A: Solving problems involving fractions and mixed numbers requires converting the mixed number to an improper fraction, while solving problems involving only fractions does not require this step.</p> <h2><strong>Q: How do I use fractions in real-life situations?</strong></h2> <p>A: Fractions are used in many real-life situations, such as cooking, measuring, and building.</p> <h2><strong>Q: What are some common applications of fractions in real-life situations?</strong></h2> <p>A: Some common applications of fractions in real-life situations include measuring ingredients for recipes, calculating the area of a room, and determining the cost of a product.</p> <h2><strong>Q: How do I use fractions to solve problems in science and engineering?</strong></h2> <p>A: Fractions are used in many scientific and engineering applications, such as calculating the volume of a container, determining the speed of an object, and measuring the area of a surface.</p> <h2><strong>Q: What are some common applications of fractions in science and engineering?</strong></h2> <p>A: Some common applications of fractions in science and engineering include calculating the volume of a container, determining the speed of an object, and measuring the area of a surface.</p> <h2><strong>Q: How do I use fractions to solve problems in finance and economics?</strong></h2> <p>A: Fractions are used in many financial and economic applications, such as calculating interest rates, determining the value of a stock, and measuring the cost of a product.</p> <h2><strong>Q: What are some common applications of fractions in finance and economics?</strong></h2> <p>A: Some common applications of fractions in finance and economics include calculating interest rates, determining the value of a stock, and measuring the cost of a product.</p> <h2><strong>References</strong></h2> <ul> <li>[1] Khan Academy. (n.d.). Greatest Common Divisor (GCD). Retrieved from <a href="https://www.khanacademy.org/math/pre-algebra/pre-algebra-fractions/pre-algebra-gcd">https://www.khanacademy.org/math/pre-algebra/pre-algebra-fractions/pre-algebra-gcd</a></li> <li>[2] Math Open Reference. (n.d.). Greatest Common Divisor (GCD). Retrieved from <a href="https://www.mathopenref.com/gcd.html">https://www.mathopenref.com/gcd.html</a></li> <li>[3] Wolfram MathWorld. (n.d.). Greatest Common Divisor. Retrieved from <a href="https://mathworld.wolfram.com/GreatestCommonDivisor.html">https://mathworld.wolfram.com/GreatestCommonDivisor.html</a></li> </ul> <h2><strong>Glossary</strong></h2> <ul> <li><strong>Greatest Common Divisor (GCD):</strong> The largest number that divides both numbers without leaving a remainder.</li> <li><strong>Numerator:</strong> The top number in a fraction.</li> <li><strong>Denominator:</strong> The bottom number in a fraction.</li> <li><strong>Fraction:</strong> A way to represent a part of a whole.</li> <li><strong>Lowest Terms:</strong> A fraction that has been simplified by dividing both numbers by their greatest common divisor.</li> <li><strong>Least Common Multiple (LCM):</strong> The smallest number that is a multiple of both numbers.</li> <li><strong>Mixed Number:</strong> A number that is a combination of a whole number and a fraction.</li> <li><strong>Improper Fraction:</strong> A fraction where the numerator is greater than or equal to the denominator.</li> <li><strong>Proper Fraction:</strong> A fraction where the numerator is less than the denominator.</li> </ul>