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2 <p>Last updated on<strong>September 18, 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 the items equally, to group or arrange items, and schedule events. In this topic, we will learn about the GCF of 20 and 80.</p>

4 <h2>What is the GCF of 20 and 80?</h2>

5 <p>The<a>greatest common factor</a><a>of</a>20 and 80 is 20. The largest<a>divisor</a>of two or more<a>numbers</a>is called the GCF of the number. If two numbers are co-prime, they have no common factors other than 1, so their GCF is 1.</p>

6 <p>The GCF of two numbers cannot be negative because divisors are always positive.</p>

7 <h2>How to find the GCF of 20 and 80?</h2>

8 <p>To find the GCF of 20 and 80, a few methods are described below </p>

9 <ul><li>Listing Factors </li>

10 <li>Prime Factorization </li>

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

12 </ul><h2>GCF of 20 and 80 by Using Listing of Factors</h2>

13 <p>Steps to find the GCF of 20 and 80 using the listing of<a>factors</a>:</p>

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

15 <p>Factors of 20 = 1, 2, 4, 5, 10, 20.</p>

16 <p>Factors of 80 = 1, 2, 4, 5, 8, 10, 16, 20, 40, 80.</p>

17 <p><strong>Step 2:</strong>Now, identify the<a>common factors</a>of them Common factors of 20 and 80: 1, 2, 4, 5, 10, 20.</p>

18 <p><strong>Step 3:</strong>Choose the largest factor The largest factor that both numbers have is 20. The GCF of 20 and 80 is 20.</p>

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21 <h2>GCF of 20 and 80 Using Prime Factorization</h2>

20 <h2>GCF of 20 and 80 Using Prime Factorization</h2>

22 <p>To find the GCF of 20 and 80 using the Prime Factorization Method, follow these steps:</p>

21 <p>To find the GCF of 20 and 80 using the Prime Factorization Method, follow these steps:</p>

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

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

24 <p>Prime Factors of 20: 20 = 2 × 2 × 5 = 2² × 5</p>

23 <p>Prime Factors of 20: 20 = 2 × 2 × 5 = 2² × 5</p>

25 <p>Prime Factors of 80: 80 = 2 × 2 × 2 × 2 × 5 = 2⁴ × 5</p>

24 <p>Prime Factors of 80: 80 = 2 × 2 × 2 × 2 × 5 = 2⁴ × 5</p>

26 <p><strong>Step 2:</strong>Now, identify the common prime factors The common prime factors are: 2 × 2 × 5 = 2² × 5</p>

25 <p><strong>Step 2:</strong>Now, identify the common prime factors The common prime factors are: 2 × 2 × 5 = 2² × 5</p>

27 <p><strong>Step 3:</strong>Multiply the common prime factors 2² × 5 = 4 × 5 = 20. The Greatest Common Factor of 20 and 80 is 20.</p>

26 <p><strong>Step 3:</strong>Multiply the common prime factors 2² × 5 = 4 × 5 = 20. The Greatest Common Factor of 20 and 80 is 20.</p>

28 <h2>GCF of 20 and 80 Using Division Method or Euclidean Algorithm Method</h2>

27 <h2>GCF of 20 and 80 Using Division Method or Euclidean Algorithm Method</h2>

29 <p>Find the GCF of 20 and 80 using the<a>division</a>method or Euclidean Algorithm Method. Follow these steps:</p>

28 <p>Find the GCF of 20 and 80 using the<a>division</a>method or Euclidean Algorithm Method. Follow these steps:</p>

30 <p><strong>Step 1:</strong>First, divide the larger number by the smaller number Here, divide 80 by 20 80 ÷ 20 = 4 (<a>quotient</a>), The<a>remainder</a>is calculated as 80 - (20×4) = 0</p>

29 <p><strong>Step 1:</strong>First, divide the larger number by the smaller number Here, divide 80 by 20 80 ÷ 20 = 4 (<a>quotient</a>), The<a>remainder</a>is calculated as 80 - (20×4) = 0</p>

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

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

32 <p>The GCF of 20 and 80 is 20.</p>

31 <p>The GCF of 20 and 80 is 20.</p>

33 <h2>Common Mistakes and How to Avoid Them in GCF of 20 and 80</h2>

32 <h2>Common Mistakes and How to Avoid Them in GCF of 20 and 80</h2>

34 <p>Finding GCF of 20 and 80 looks simple, but students often make mistakes while calculating the GCF. Here are some common mistakes to be avoided by the students.</p>

33 <p>Finding GCF of 20 and 80 looks simple, but students often make mistakes while calculating the GCF. Here are some common mistakes to be avoided by the students.</p>

35 <h3>Problem 1</h3>

34 <h3>Problem 1</h3>

36 <p>A teacher has 20 apples and 80 oranges. 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>

35 <p>A teacher has 20 apples and 80 oranges. 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>

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

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

38 <p>We should find GCF of 20 and 80 GCF of 20 and 80 2² × 5 = 4 × 5 = 20.</p>

37 <p>We should find GCF of 20 and 80 GCF of 20 and 80 2² × 5 = 4 × 5 = 20.</p>

39 <p>There are 20 equal groups 20 ÷ 20 = 1 80 ÷ 20 = 4</p>

38 <p>There are 20 equal groups 20 ÷ 20 = 1 80 ÷ 20 = 4</p>

40 <p>There will be 20 groups, and each group gets 1 apple and 4 oranges.</p>

39 <p>There will be 20 groups, and each group gets 1 apple and 4 oranges.</p>

41 <h3>Explanation</h3>

40 <h3>Explanation</h3>

42 <p>As the GCF of 20 and 80 is 20, the teacher can make 20 groups.</p>

41 <p>As the GCF of 20 and 80 is 20, the teacher can make 20 groups.</p>

43 <p>Now divide 20 and 80 by 20.</p>

42 <p>Now divide 20 and 80 by 20.</p>

44 <p>Each group gets 1 apple and 4 oranges.</p>

43 <p>Each group gets 1 apple and 4 oranges.</p>

45 <p>Well explained 👍</p>

44 <p>Well explained 👍</p>

46 <h3>Problem 2</h3>

45 <h3>Problem 2</h3>

47 <p>A school has 20 red flags and 80 blue flags. They want to arrange them in rows with the same number of flags in each row, using the largest possible number of flags per row. How many flags will be in each row?</p>

46 <p>A school has 20 red flags and 80 blue flags. They want to arrange them in rows with the same number of flags in each row, using the largest possible number of flags per row. How many flags will be in each row?</p>

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

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

49 <p>GCF of 20 and 80 2² × 5 = 4 × 5 = 20. So each row will have 20 flags.</p>

48 <p>GCF of 20 and 80 2² × 5 = 4 × 5 = 20. So each row will have 20 flags.</p>

50 <h3>Explanation</h3>

49 <h3>Explanation</h3>

51 <p>There are 20 red and 80 blue flags.</p>

50 <p>There are 20 red and 80 blue flags.</p>

52 <p>To find the total number of flags in each row, we should find the GCF of 20 and 80.</p>

51 <p>To find the total number of flags in each row, we should find the GCF of 20 and 80.</p>

53 <p>There will be 20 flags in each row.</p>

52 <p>There will be 20 flags in each row.</p>

54 <p>Well explained 👍</p>

53 <p>Well explained 👍</p>

55 <h3>Problem 3</h3>

54 <h3>Problem 3</h3>

56 <p>A tailor has 20 meters of red fabric and 80 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>

55 <p>A tailor has 20 meters of red fabric and 80 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>

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

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

58 <p>For calculating the longest equal length, we have to calculate the GCF of 20 and 80</p>

57 <p>For calculating the longest equal length, we have to calculate the GCF of 20 and 80</p>

59 <p>The GCF of 20 and 80 2² × 5 = 4 × 5 = 20.</p>

58 <p>The GCF of 20 and 80 2² × 5 = 4 × 5 = 20.</p>

60 <p>The fabric is 20 meters long.</p>

59 <p>The fabric is 20 meters long.</p>

61 <h3>Explanation</h3>

60 <h3>Explanation</h3>

62 <p>For calculating the longest length of the fabric, first, we need to calculate the GCF of 20 and 80, which is 20.</p>

61 <p>For calculating the longest length of the fabric, first, we need to calculate the GCF of 20 and 80, which is 20.</p>

63 <p>The length of each piece of fabric will be 20 meters.</p>

62 <p>The length of each piece of fabric will be 20 meters.</p>

64 <p>Well explained 👍</p>

63 <p>Well explained 👍</p>

65 <h3>Problem 4</h3>

64 <h3>Problem 4</h3>

66 <p>A carpenter has two wooden planks, one 20 cm long and the other 80 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>

65 <p>A carpenter has two wooden planks, one 20 cm long and the other 80 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>

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

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

68 <p>The carpenter needs the longest piece of wood GCF of 20 and 80 2² × 5 = 4 × 5 = 20.</p>

67 <p>The carpenter needs the longest piece of wood GCF of 20 and 80 2² × 5 = 4 × 5 = 20.</p>

69 <p>The longest length of each piece is 20 cm.</p>

68 <p>The longest length of each piece is 20 cm.</p>

70 <h3>Explanation</h3>

69 <h3>Explanation</h3>

71 <p>To find the longest length of each piece of the two wooden planks, 20 cm and 80 cm, respectively.</p>

70 <p>To find the longest length of each piece of the two wooden planks, 20 cm and 80 cm, respectively.</p>

72 <p>We have to find the GCF of 20 and 80, which is 20 cm.</p>

71 <p>We have to find the GCF of 20 and 80, which is 20 cm.</p>

73 <p>The longest length of each piece is 20 cm.</p>

72 <p>The longest length of each piece is 20 cm.</p>

74 <p>Well explained 👍</p>

73 <p>Well explained 👍</p>

75 <h3>Problem 5</h3>

74 <h3>Problem 5</h3>

76 <p>If the GCF of 20 and ‘b’ is 20, and the LCM is 160, find ‘b’.</p>

75 <p>If the GCF of 20 and ‘b’ is 20, and the LCM is 160, find ‘b’.</p>

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

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

78 <p>The value of ‘b’ is 80.</p>

77 <p>The value of ‘b’ is 80.</p>

79 <h3>Explanation</h3>

78 <h3>Explanation</h3>

80 <p>GCF × LCM = product of the numbers</p>

79 <p>GCF × LCM = product of the numbers</p>

81 <p>20 × 160 = 20 × b</p>

80 <p>20 × 160 = 20 × b</p>

82 <p>3200 = 20b</p>

81 <p>3200 = 20b</p>

83 <p>b = 3200 ÷ 20 = 80</p>

82 <p>b = 3200 ÷ 20 = 80</p>

84 <p>Well explained 👍</p>

83 <p>Well explained 👍</p>

85 <h2>FAQs on the Greatest Common Factor of 20 and 80</h2>

84 <h2>FAQs on the Greatest Common Factor of 20 and 80</h2>

86 <h3>1.What is the LCM of 20 and 80?</h3>

85 <h3>1.What is the LCM of 20 and 80?</h3>

87 <p>The LCM of 20 and 80 is 80.</p>

86 <p>The LCM of 20 and 80 is 80.</p>

88 <h3>2.Is 20 divisible by 5?</h3>

87 <h3>2.Is 20 divisible by 5?</h3>

89 <p>Yes, 20 is divisible by 5 because 20 ÷ 5 = 4.</p>

88 <p>Yes, 20 is divisible by 5 because 20 ÷ 5 = 4.</p>

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

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

91 <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>

90 <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>

92 <h3>4.What is the prime factorization of 80?</h3>

91 <h3>4.What is the prime factorization of 80?</h3>

93 <p>The prime factorization of 80 is 2⁴ × 5.</p>

92 <p>The prime factorization of 80 is 2⁴ × 5.</p>

94 <h3>5.Are 20 and 80 prime numbers?</h3>

93 <h3>5.Are 20 and 80 prime numbers?</h3>

95 <p>No, 20 and 80 are not prime numbers because both of them have more than two factors.</p>

94 <p>No, 20 and 80 are not prime numbers because both of them have more than two factors.</p>

96 <h2>Important Glossaries for GCF of 20 and 80</h2>

95 <h2>Important Glossaries for GCF of 20 and 80</h2>

97 <ul><li><strong>Factors:</strong>Factors are numbers that divide the target number completely. For example, the factors of 20 are 1, 2, 4, 5, 10, and 20.</li>

96 <ul><li><strong>Factors:</strong>Factors are numbers that divide the target number completely. For example, the factors of 20 are 1, 2, 4, 5, 10, and 20.</li>

98 </ul><ul><li><strong>Multiple:</strong>Multiples are the products we get by multiplying a given number by another. For example, the multiples of 5 are 5, 10, 15, 20, 25, and so on.</li>

97 </ul><ul><li><strong>Multiple:</strong>Multiples are the products we get by multiplying a given number by another. For example, the multiples of 5 are 5, 10, 15, 20, 25, and so on.</li>

99 </ul><ul><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 20 are 2 and 5.</li>

98 </ul><ul><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 20 are 2 and 5.</li>

100 </ul><ul><li><strong>Remainder:</strong>The value left after division when the number cannot be divided evenly. For example, when 20 is divided by 6, the remainder is 2 and the quotient is 3.</li>

99 </ul><ul><li><strong>Remainder:</strong>The value left after division when the number cannot be divided evenly. For example, when 20 is divided by 6, the remainder is 2 and the quotient is 3.</li>

101 </ul><ul><li><strong>LCM:</strong>The smallest common multiple of two or more numbers is termed LCM. For example, the LCM of 20 and 80 is 80.</li>

100 </ul><ul><li><strong>LCM:</strong>The smallest common multiple of two or more numbers is termed LCM. For example, the LCM of 20 and 80 is 80.</li>

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

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

103 <p>▶</p>

102 <p>▶</p>

104 <h2>Hiralee Lalitkumar Makwana</h2>

103 <h2>Hiralee Lalitkumar Makwana</h2>

105 <h3>About the Author</h3>

104 <h3>About the Author</h3>

106 <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>

105 <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>

107 <h3>Fun Fact</h3>

106 <h3>Fun Fact</h3>

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

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