What is the GCF of 45 and 20?
Understand the Problem
The question is asking to find the greatest common factor (GCF) of the two numbers 45 and 20. This involves determining the largest integer that divides both numbers without leaving a remainder.
Answer
The GCF of 45 and 20 is $5$.
Answer for screen readers
The greatest common factor (GCF) of 45 and 20 is $5$.
Steps to Solve
- List the Factors of Each Number
First, we find all the factors of both numbers.
- For 45, the factors are: 1, 3, 5, 9, 15, 45
- For 20, the factors are: 1, 2, 4, 5, 10, 20
- Identify the Common Factors
Next, we determine which factors are common to both lists.
Common factors of 45 and 20 are: 1, 5
- Find the Greatest Common Factor
From the common factors identified, we choose the largest one.
The largest common factor is 5.
The greatest common factor (GCF) of 45 and 20 is $5$.
More Information
The GCF is useful in many areas of mathematics, including simplifying fractions and solving problems involving ratios. It's the highest number that can evenly divide both numbers.
Tips
- Not Listing All Factors: Sometimes, people miss some of the factors. Make sure to list all of them carefully.
- Forgetting to Compare Common Factors: Always check all factors for commonality. It can be easy to overlook smaller numbers.
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