What is the greatest common factor (GCF) for 21 and 40?
Understand the Problem
The question is asking for the greatest common factor (GCF) of the numbers 21 and 40. To solve this, we will identify the factors of each number and determine the largest factor they share.
Answer
The GCF of 21 and 40 is $1$.
Answer for screen readers
The greatest common factor of 21 and 40 is 1.
Steps to Solve
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List the factors of 21 Start by identifying all the factors of the number 21. The factors are: 1, 3, 7, 21.
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List the factors of 40 Next, identify all the factors of the number 40. The factors are: 1, 2, 4, 5, 8, 10, 20, 40.
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Find the common factors Compare the factors of both numbers and list the common factors. The common factors between 21 and 40 are: 1.
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Identify the greatest common factor From the common factors identified, the greatest common factor is the largest one. Therefore, the GCF is 1.
The greatest common factor of 21 and 40 is 1.
More Information
The GCF is useful in various areas of math, particularly in simplifying fractions, finding common denominators, and solving problems that involve ratios.
Tips
- A common mistake is assuming that the GCF is larger than 1 without checking the factors thoroughly. Make sure to list all factors to avoid this error.
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