Answer: D) 24
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Explanation:
Find the prime factorization of each value given
- 28 = 2*2*7
- 15 = 3*5
- 21 = 3*7
- 24 = 2*2*3
Of the four choices, only 24 has 2*3 = 6 as a factor. Something like 15 doesn't have 6 as a factor, so there's no way the GCF of 15 and 18 is equal to 6.
Focusing on 24 and 18, we see that
which shows that 6 is the GCF of 24 and 18.
