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If 15 and 4 are factors of positive integer K, and 5 and 8 a

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GRE Instructor
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Joined: 10 Apr 2015
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Kudos [?]: 1055 [0], given: 6

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If 15 and 4 are factors of positive integer K, and 5 and 8 a [#permalink] New post 26 May 2017, 13:37
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Question Stats:

50% (01:57) correct 50% (02:05) wrong based on 8 sessions
If 15 and 4 are factors of positive integer K, and 5 and 8 are not factors of positive integer M, then K – M CANNOT equal

A) 34
B) 44
C) 54
D) 70
E) 83
[Reveal] Spoiler: OA

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GRE Instructor
User avatar
Joined: 10 Apr 2015
Posts: 1182
Followers: 44

Kudos [?]: 1055 [0], given: 6

CAT Tests
Re: If 15 and 4 are factors of positive integer K, and 5 and 8 a [#permalink] New post 05 Jun 2017, 13:25
Expert's post
GreenlightTestPrep wrote:
If 15 and 4 are factors of positive integer K, and 5 and 8 are not factors of positive integer M, then K – M CANNOT equal

A) 34
B) 44
C) 54
D) 70
E) 83


RULE #1: If d is a divisor/factor of x, but d is NOT a divisor/factor of y, then d is NOT a divisor/factor of x+y
RULE #2: If d is a divisor/factor of x, but d is NOT a divisor/factor of y, then d is NOT a divisor/factor of x-y


If 15 is a factor of K, then we can also be certain that 5 is a factor of K.
So, we know that 5 is a factor of K AND we know that 5 is not a factor of M
By RULE #2, we know that 5 is not a factor of K - M
So, K-M cannot equal 70

Answer:
[Reveal] Spoiler:
D

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Brent Hanneson – Creator of greenlighttestprep.com
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Re: If 15 and 4 are factors of positive integer K, and 5 and 8 a   [#permalink] 05 Jun 2017, 13:25
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If 15 and 4 are factors of positive integer K, and 5 and 8 a

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