Explanation
Find the factors of 24: 1 and 24, 2 and 12, 3 and 8, and 4 and 6. Now begin to use the outside to inside method to find the common factors of 48. The first pair is 1 and 48. Since 48 is not a factor of 24, it is not the GCF. The next pair is 2 and 24. Since 24 is also a factor of 24, it is a common factor. The only greater factor of 48 is 48, which is not a common factor. Therefore, the greatest common factor of 24 and 48 must be 24.