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2 <p>Last updated on<strong>August 5, 2025</strong></p>

3 <p>The GCF is the largest number that can divide two or more numbers without leaving any remainder. GCF is used to share items equally, to group or arrange items, and to schedule events. In this topic, we will learn about the GCF of 18 and 45.</p>

4 <h2>What is the GCF of 18 and 45?</h2>

5 <p>The<a>greatest common factor</a><a>of</a>18 and 45 is 9. The largest<a>divisor</a>of two or more<a>numbers</a>is called the GCF of the numbers. If two numbers are co-prime, they have no common factors other than 1, so their GCF is 1. The GCF of two numbers cannot be negative because divisors are always positive.</p>

6 <h2>How to find the GCF of 18 and 45?</h2>

7 <p>To find the GCF of 18 and 45, a few methods are described below</p>

8 <ul><li>Listing Factors</li>

9 <li>Prime Factorization</li>

10 <li>Long Division Method / by Euclidean Algorithm</li>

11 </ul><h2>GCF of 18 and 45 by Using Listing of Factors</h2>

12 <p>Steps to find the GCF of 18 and 45 using the listing of<a>factors</a></p>

13 <p><strong>Step 1:</strong>Firstly, list the factors of each number</p>

14 <p>Factors of 18 = 1, 2, 3, 6, 9, 18.</p>

15 <p>Factors of 45 = 1, 3, 5, 9, 15, 45.</p>

16 <p><strong>Step 2:</strong>Now, identify the<a>common factors</a>of them Common factors of 18 and 45: 1, 3, 9.</p>

17 <p><strong>Step 3:</strong>Choose the largest factor</p>

18 <p>The largest factor that both numbers have is 9.</p>

19 <p>The GCF of 18 and 45 is 9.</p>

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22 <h2>GCF of 18 and 45 Using Prime Factorization</h2>

21 <h2>GCF of 18 and 45 Using Prime Factorization</h2>

23 <p>To find the GCF of 18 and 45 using the Prime Factorization Method, follow these steps:</p>

22 <p>To find the GCF of 18 and 45 using the Prime Factorization Method, follow these steps:</p>

24 <p><strong>Step 1:</strong>Find the<a>prime factors</a>of each number</p>

23 <p><strong>Step 1:</strong>Find the<a>prime factors</a>of each number</p>

25 <p>Prime Factors of 18: 18 = 2 × 3 × 3 = 2 × 3²</p>

24 <p>Prime Factors of 18: 18 = 2 × 3 × 3 = 2 × 3²</p>

26 <p>Prime Factors of 45: 45 = 3 × 3 × 5 = 3² × 5</p>

25 <p>Prime Factors of 45: 45 = 3 × 3 × 5 = 3² × 5</p>

27 <p><strong>Step 2:</strong>Now, identify the common prime factors</p>

26 <p><strong>Step 2:</strong>Now, identify the common prime factors</p>

28 <p>The common prime factors are: 3 × 3 = 3²</p>

27 <p>The common prime factors are: 3 × 3 = 3²</p>

29 <p><strong>Step 3:</strong>Multiply the common prime factors 3² = 9.</p>

28 <p><strong>Step 3:</strong>Multiply the common prime factors 3² = 9.</p>

30 <p>The Greatest Common Factor of 18 and 45 is 9.</p>

29 <p>The Greatest Common Factor of 18 and 45 is 9.</p>

31 <h2>GCF of 18 and 45 Using Division Method or Euclidean Algorithm Method</h2>

30 <h2>GCF of 18 and 45 Using Division Method or Euclidean Algorithm Method</h2>

32 <p>Find the GCF of 18 and 45 using the<a>division</a>method or Euclidean Algorithm Method. Follow these steps:</p>

31 <p>Find the GCF of 18 and 45 using the<a>division</a>method or Euclidean Algorithm Method. Follow these steps:</p>

33 <p><strong>Step 1:</strong>First, divide the larger number by the smaller number</p>

32 <p><strong>Step 1:</strong>First, divide the larger number by the smaller number</p>

34 <p>Here, divide 45 by 18 45 ÷ 18 = 2 (<a>quotient</a>),</p>

33 <p>Here, divide 45 by 18 45 ÷ 18 = 2 (<a>quotient</a>),</p>

35 <p>The<a>remainder</a>is calculated as 45 - (18×2) = 9</p>

34 <p>The<a>remainder</a>is calculated as 45 - (18×2) = 9</p>

36 <p>The remainder is 9, not zero, so continue the process</p>

35 <p>The remainder is 9, not zero, so continue the process</p>

37 <p><strong>Step 2:</strong>Now divide the previous divisor (18) by the previous remainder (9)</p>

36 <p><strong>Step 2:</strong>Now divide the previous divisor (18) by the previous remainder (9)</p>

38 <p>Divide 18 by 9 18 ÷ 9 = 2 (quotient), remainder = 18 - (9×2) = 0</p>

37 <p>Divide 18 by 9 18 ÷ 9 = 2 (quotient), remainder = 18 - (9×2) = 0</p>

39 <p>The remainder is zero, the divisor will become the GCF.</p>

38 <p>The remainder is zero, the divisor will become the GCF.</p>

40 <p>The GCF of 18 and 45 is 9.</p>

39 <p>The GCF of 18 and 45 is 9.</p>

41 <h2>Common Mistakes and How to Avoid Them in GCF of 18 and 45</h2>

40 <h2>Common Mistakes and How to Avoid Them in GCF of 18 and 45</h2>

42 <p>Finding the GCF of 18 and 45 looks simple, but students often make mistakes while calculating the GCF. Here are some common mistakes to be avoided by the students.</p>

41 <p>Finding the GCF of 18 and 45 looks simple, but students often make mistakes while calculating the GCF. Here are some common mistakes to be avoided by the students.</p>

43 <h3>Problem 1</h3>

42 <h3>Problem 1</h3>

44 <p>A teacher has 18 books and 45 notebooks. She wants to group them into equal sets, with the largest number of items in each group. How many items will be in each group?</p>

43 <p>A teacher has 18 books and 45 notebooks. She wants to group them into equal sets, with the largest number of items in each group. How many items will be in each group?</p>

45 <p>Okay, lets begin</p>

44 <p>Okay, lets begin</p>

46 <p>We should find the GCF of 18 and 45 GCF of 18 and 45 3² = 9.</p>

45 <p>We should find the GCF of 18 and 45 GCF of 18 and 45 3² = 9.</p>

47 <p>There are 9 equal groups 18 ÷ 9 = 2 45 ÷ 9 = 5</p>

46 <p>There are 9 equal groups 18 ÷ 9 = 2 45 ÷ 9 = 5</p>

48 <p>There will be 9 groups, and each group gets 2 books and 5 notebooks.</p>

47 <p>There will be 9 groups, and each group gets 2 books and 5 notebooks.</p>

49 <h3>Explanation</h3>

48 <h3>Explanation</h3>

50 <p>As the GCF of 18 and 45 is 9, the teacher can make 9 groups.</p>

49 <p>As the GCF of 18 and 45 is 9, the teacher can make 9 groups.</p>

51 <p>Now divide 18 and 45 by 9.</p>

50 <p>Now divide 18 and 45 by 9.</p>

52 <p>Each group gets 2 books and 5 notebooks.</p>

51 <p>Each group gets 2 books and 5 notebooks.</p>

53 <p>Well explained 👍</p>

52 <p>Well explained 👍</p>

54 <h3>Problem 2</h3>

53 <h3>Problem 2</h3>

55 <p>A school has 18 red chairs and 45 blue chairs. They want to arrange them in rows with the same number of chairs in each row, using the largest possible number of chairs per row. How many chairs will be in each row?</p>

54 <p>A school has 18 red chairs and 45 blue chairs. They want to arrange them in rows with the same number of chairs in each row, using the largest possible number of chairs per row. How many chairs will be in each row?</p>

56 <p>Okay, lets begin</p>

55 <p>Okay, lets begin</p>

57 <p>GCF of 18 and 45 3² = 9. So each row will have 9 chairs.</p>

56 <p>GCF of 18 and 45 3² = 9. So each row will have 9 chairs.</p>

58 <h3>Explanation</h3>

57 <h3>Explanation</h3>

59 <p>There are 18 red and 45 blue chairs.</p>

58 <p>There are 18 red and 45 blue chairs.</p>

60 <p>To find the total number of chairs in each row, we should find the GCF of 18 and 45.</p>

59 <p>To find the total number of chairs in each row, we should find the GCF of 18 and 45.</p>

61 <p>There will be 9 chairs in each row.</p>

60 <p>There will be 9 chairs in each row.</p>

62 <p>Well explained 👍</p>

61 <p>Well explained 👍</p>

63 <h3>Problem 3</h3>

62 <h3>Problem 3</h3>

64 <p>A tailor has 18 meters of red fabric and 45 meters of blue fabric. She wants to cut both fabrics into pieces of equal length, using the longest possible length. What should be the length of each piece?</p>

63 <p>A tailor has 18 meters of red fabric and 45 meters of blue fabric. She wants to cut both fabrics into pieces of equal length, using the longest possible length. What should be the length of each piece?</p>

65 <p>Okay, lets begin</p>

64 <p>Okay, lets begin</p>

66 <p>For calculating the longest equal length, we have to calculate the GCF of 18 and 45</p>

65 <p>For calculating the longest equal length, we have to calculate the GCF of 18 and 45</p>

67 <p>The GCF of 18 and 45 3² = 9.</p>

66 <p>The GCF of 18 and 45 3² = 9.</p>

68 <p>The fabric is 9 meters long.</p>

67 <p>The fabric is 9 meters long.</p>

69 <h3>Explanation</h3>

68 <h3>Explanation</h3>

70 <p>For calculating the longest length of the fabric first we need to calculate the GCF of 18 and 45 which is 9.</p>

69 <p>For calculating the longest length of the fabric first we need to calculate the GCF of 18 and 45 which is 9.</p>

71 <p>The length of each piece of fabric will be 9 meters.</p>

70 <p>The length of each piece of fabric will be 9 meters.</p>

72 <p>Well explained 👍</p>

71 <p>Well explained 👍</p>

73 <h3>Problem 4</h3>

72 <h3>Problem 4</h3>

74 <p>A carpenter has two wooden planks, one 18 cm long and the other 45 cm long. He wants to cut them into the longest possible equal pieces, without any wood left over. What should be the length of each piece?</p>

73 <p>A carpenter has two wooden planks, one 18 cm long and the other 45 cm long. He wants to cut them into the longest possible equal pieces, without any wood left over. What should be the length of each piece?</p>

75 <p>Okay, lets begin</p>

74 <p>Okay, lets begin</p>

76 <p>The carpenter needs the longest piece of wood GCF of 18 and 45 3² = 9.</p>

75 <p>The carpenter needs the longest piece of wood GCF of 18 and 45 3² = 9.</p>

77 <p>The longest length of each piece is 9 cm.</p>

76 <p>The longest length of each piece is 9 cm.</p>

78 <h3>Explanation</h3>

77 <h3>Explanation</h3>

79 <p>To find the longest length of each piece of the two wooden planks, 18 cm and 45 cm, respectively.</p>

78 <p>To find the longest length of each piece of the two wooden planks, 18 cm and 45 cm, respectively.</p>

80 <p>We have to find the GCF of 18 and 45, which is 9 cm.</p>

79 <p>We have to find the GCF of 18 and 45, which is 9 cm.</p>

81 <p>The longest length of each piece is 9 cm.</p>

80 <p>The longest length of each piece is 9 cm.</p>

82 <p>Well explained 👍</p>

81 <p>Well explained 👍</p>

83 <h3>Problem 5</h3>

82 <h3>Problem 5</h3>

84 <p>If the GCF of 18 and ‘a’ is 9, and the LCM is 90, find ‘a’.</p>

83 <p>If the GCF of 18 and ‘a’ is 9, and the LCM is 90, find ‘a’.</p>

85 <p>Okay, lets begin</p>

84 <p>Okay, lets begin</p>

86 <p>The value of ‘a’ is 45.</p>

85 <p>The value of ‘a’ is 45.</p>

87 <h3>Explanation</h3>

86 <h3>Explanation</h3>

88 <p>GCF × LCM = product of the numbers 9 × 90 = 18 × a</p>

87 <p>GCF × LCM = product of the numbers 9 × 90 = 18 × a</p>

89 <p>810 = 18a</p>

88 <p>810 = 18a</p>

90 <p>a = 810 ÷ 18 = 45</p>

89 <p>a = 810 ÷ 18 = 45</p>

91 <p>Well explained 👍</p>

90 <p>Well explained 👍</p>

92 <h2>FAQs on the Greatest Common Factor of 18 and 45</h2>

91 <h2>FAQs on the Greatest Common Factor of 18 and 45</h2>

93 <h3>1.What is the LCM of 18 and 45?</h3>

92 <h3>1.What is the LCM of 18 and 45?</h3>

94 <p>The LCM of 18 and 45 is 90.</p>

93 <p>The LCM of 18 and 45 is 90.</p>

95 <h3>2.Is 18 divisible by 2?</h3>

94 <h3>2.Is 18 divisible by 2?</h3>

96 <p>Yes, 18 is divisible by 2 because it is an even number.</p>

95 <p>Yes, 18 is divisible by 2 because it is an even number.</p>

97 <h3>3.What will be the GCF of any two prime numbers?</h3>

96 <h3>3.What will be the GCF of any two prime numbers?</h3>

98 <p>The common factor of<a>prime numbers</a>is 1 and the number itself. Since 1 is the only common factor of any two prime numbers, it is said to be the GCF of any two prime numbers.</p>

97 <p>The common factor of<a>prime numbers</a>is 1 and the number itself. Since 1 is the only common factor of any two prime numbers, it is said to be the GCF of any two prime numbers.</p>

99 <h3>4.What is the prime factorization of 45?</h3>

98 <h3>4.What is the prime factorization of 45?</h3>

100 <p>The prime factorization of 45 is 3² × 5.</p>

99 <p>The prime factorization of 45 is 3² × 5.</p>

101 <h3>5.Are 18 and 45 prime numbers?</h3>

100 <h3>5.Are 18 and 45 prime numbers?</h3>

102 <p>No, 18 and 45 are not prime numbers because both of them have more than two factors.</p>

101 <p>No, 18 and 45 are not prime numbers because both of them have more than two factors.</p>

103 <h2>Important Glossaries for GCF of 18 and 45</h2>

102 <h2>Important Glossaries for GCF of 18 and 45</h2>

104 <ul><li><strong>Factors:</strong>Factors are numbers that divide the target number completely. For example, the factors of 9 are 1, 3, and 9.</li>

103 <ul><li><strong>Factors:</strong>Factors are numbers that divide the target number completely. For example, the factors of 9 are 1, 3, and 9.</li>

105 <li><strong>Multiple:</strong>Multiples are the products we get by multiplying a given number by another. For example, the multiples of 3 are 3, 6, 9, 12, and so on.</li>

104 <li><strong>Multiple:</strong>Multiples are the products we get by multiplying a given number by another. For example, the multiples of 3 are 3, 6, 9, 12, and so on.</li>

106 <li><strong>Prime Factors:</strong>These are the factors of a number that are prime numbers and divide the given number completely. For example, the prime factors of 18 are 2 and 3.</li>

105 <li><strong>Prime Factors:</strong>These are the factors of a number that are prime numbers and divide the given number completely. For example, the prime factors of 18 are 2 and 3.</li>

107 <li><strong>Remainder:</strong>The value left after division when the number cannot be divided evenly. For example, when 45 is divided by 7, the remainder is 3 and the quotient is 6.</li>

106 <li><strong>Remainder:</strong>The value left after division when the number cannot be divided evenly. For example, when 45 is divided by 7, the remainder is 3 and the quotient is 6.</li>

108 <li><strong>LCM:</strong>The smallest common multiple of two or more numbers is termed LCM. For example, the LCM of 18 and 45 is 90.</li>

107 <li><strong>LCM:</strong>The smallest common multiple of two or more numbers is termed LCM. For example, the LCM of 18 and 45 is 90.</li>

109 <li><strong>GCF:</strong>The largest factor that commonly divides two or more numbers. For example, the GCF of 18 and 45 is 9 as it is their largest common factor that divides the numbers completely.</li>

108 <li><strong>GCF:</strong>The largest factor that commonly divides two or more numbers. For example, the GCF of 18 and 45 is 9 as it is their largest common factor that divides the numbers completely.</li>

110 </ul><p>What Are Numbers? 🔢 | Fun Explanation with 🎯 Real-Life Examples for Kids | ✨BrightCHAMPS Math</p>

109 </ul><p>What Are Numbers? 🔢 | Fun Explanation with 🎯 Real-Life Examples for Kids | ✨BrightCHAMPS Math</p>

111 <p>▶</p>

110 <p>▶</p>

112 <h2>Hiralee Lalitkumar Makwana</h2>

111 <h2>Hiralee Lalitkumar Makwana</h2>

113 <h3>About the Author</h3>

112 <h3>About the Author</h3>

114 <p>Hiralee Lalitkumar Makwana has almost two years of teaching experience. She is a number ninja as she loves numbers. Her interest in numbers can be seen in the way she cracks math puzzles and hidden patterns.</p>

113 <p>Hiralee Lalitkumar Makwana has almost two years of teaching experience. She is a number ninja as she loves numbers. Her interest in numbers can be seen in the way she cracks math puzzles and hidden patterns.</p>

115 <h3>Fun Fact</h3>

114 <h3>Fun Fact</h3>

116 <p>: She loves to read number jokes and games.</p>

115 <p>: She loves to read number jokes and games.</p>