gcf of 21 and 40
Understand the Problem
The question is asking to find the greatest common factor (GCF) of the numbers 21 and 40. This involves identifying the largest number that can divide both 21 and 40 without leaving a remainder.
Answer
The GCF of 21 and 40 is $1$.
Answer for screen readers
The greatest common factor (GCF) of 21 and 40 is 1.
Steps to Solve
- List the Factors of Each Number
First, we will list all the factors of 21 and 40.
- The factors of 21 are: 1, 3, 7, 21
- The factors of 40 are: 1, 2, 4, 5, 8, 10, 20, 40
- Identify the Common Factors
Next, we need to identify which factors are common to both lists of factors.
- Common factors of 21 and 40: 1
- Determine the Greatest Common Factor
Now that we have the common factors, we will select the greatest one among them.
- The greatest common factor (GCF) is 1.
The greatest common factor (GCF) of 21 and 40 is 1.
More Information
The GCF is the largest positive integer that divides the given numbers. In this case, since 21 and 40 share no other common factors except for 1, the GCF is simply 1. This indicates that 21 and 40 are relatively prime (or coprime), meaning they have no common factors other than 1.
Tips
- A common mistake is to overlook the definition of the GCF and assume it must be greater than 1. Remember that two numbers can be relatively prime, which means their GCF is 1.
