Question

The GCF of 18 and a number is 6. Which of the following could be the number?

A.28
B.15
C.21
D.24​

Answer 1

Answer: D) 24

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Step-by-step 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

• 24 = 6*4
• 18 = 6*3

which shows that 6 is the GCF of 24 and 18.