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Bunuel
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Bunuel
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ans is C..
8! can be written as 5!*6*7*8 so other given choices will increase the common factor and 5!*5 will keep GCF as 5!
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GCF is the product of common factors of the numbers involved.

GCF = 5!

a = 8! = 8*7*6*5!

b will certainly have 5! and cannot have any more common factors with a (as this will increase the GCF)

Looking at the answers only 5 (5!) and 8! will have GCF as 5!

Ans C
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You want the common factor between 8! and the other number to be exactly 5!, not anything bigger.
If the second number is written as k × 5!, then the only way the GCF stays 5! is if k does not share any factors with the extra part of 8!. The value that keeps that clean is k equal to 5.

So 5 × 5! works. Option C!
Bunuel
The greatest common factor of two numbers is 5!. Which of the following can be the second number, if one of the numbers is 8!?

A. 3(5!)
B. 4(5!)
C. 5(5!)
D. 6(5!)
E. 7(5!)
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