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# What are the greatest common factors of 21 and 28 and 56?

Updated: 10/24/2022

Wiki User

13y ago

the greatest common factor is 7,

because 21 divided by 7 is 3,

28 divided by 7 is 4

and 56 divided by 7 is 8.

Wiki User

13y ago

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Q: What are the greatest common factors of 21 and 28 and 56?
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### What ARE THE common factors and greatest common factors of 21 and 28?

The common factors are 1 and 7. The GCF is 7.

### What what is the greatest common factor 21 and 28?

The GCF of 21 and 28 is 7.One way to determine the greatest common factor is to find all the factors of the numbers and compare them.The factors of 21 are 1, 3, 7, and 21.The factors of 28 are 1, 2, 4, 7, 14, and 28.The common factors are 1 and 7. Therefore, the greatest common factor is 7.The greatest common factor can also be calculated by identifying the common prime factors and multiplying them together.The prime factors of 21 are 3 and 7.The prime factors of 28 are 2, 2, and 7.The prime factors in common are a single 7, so the greatest common factor is 7.77There is neither a greatest common factor nor common factors of a single number, such as 2821, because there cannot be any form of common factor without two or more numbers to compare. Common factors are factors that the numbers being compared have in common. The greatest common factor is the largest factor that all the numbers being compared have in common. Thus, since there are not two or more numbers to compare, there are neither common factors nor a greatest common factor.

### What is the greatest common factor of 15 21 and 28?

The Greatest Common Factor of 15, 21, 28: 1

### What are the common factors of 21 and 28?

the greatest common factor is 7, because 21 divided by 7 is 3, 28 divided by 7 is 4 and 56 divided by 7 is 8.

28

### What are the greatest common factors of 64 and 28?

The greatest common factor is 4

### What are all the common factors of 42 and 28 and state the greatest common factor?

Factors of 28... 1,2,4,7,14,28 Factors of 42... 1,2,3,6,7,14,21,42 GCF = 14

### What is the LCM of 28 and 21?

To determine the least common multiple of two numbers, determine the prime factors of both number. Then, determine the prime factors they have in common. Multiply all their prime factors together (in other words, multiply both numbers together) and divide by the prime factors they have in common (in other words, their greatest common factor). The prime factors of 21 are 3 and 7. The prime factors of 28 are 2, 2, and 7. The prime factors in common are a single 7. Therefore, the lowest common multiple is 21 x 28 &divide; 7 = 84

### What are the greatest common factor of 28 42 56?

The factors of 28 are: 1, 2, 4, 7, 14, 28.The factors of 42 are: 1, 2, 3, 6, 7, 14, 21, 42.The factors of 56 are: 1, 2, 4, 7, 8, 14, 28, 56.The common factors are: 1, 2, 7, 14The greatest common factor is 14

28

### What is the GCF of 105 and 84?

The factors of 84 are:1, 2, 3, 4, 6, 7, 12, 14, 21, 28, 42, 84The factors of 105 are:1, 3, 5, 7, 15, 21, 35, 105The common factors are:1, 3, 7, 21The Greatest Common Factor (GCF) is:21