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If p is an integer, is q an integer?

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Director
Status: Finally Done. Admitted in Kellogg for 2015 intake
Joined: 25 Jun 2011
Posts: 533

Kudos [?]: 4121 [0], given: 217

Location: United Kingdom
GMAT 1: 730 Q49 V45
GPA: 2.9
WE: Information Technology (Consulting)
If p is an integer, is q an integer? [#permalink]

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11 Feb 2012, 18:41
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25% (medium)

Question Stats:

75% (00:48) correct 25% (00:57) wrong based on 44 sessions

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If p is an integer, is q an integer?
(1) The average (arithmetic mean) of p, q, and r is p.
(2) r is an integer.

Ok - this is how I am trying to solve this.
If the average of three numbers is one of the numbers, that means the numbers are equally spaced. p + q + r = 3p
q - p = p - r. In other words, the difference between p and q is equal to the difference between p and r. That doesnt tell us if q is an integer, because you dont know anything about r.
Statement (2) is also insufficient: simply knowing that r is an integer isnt enough to tell you anything about q.
Taken together, the statements are sufficient as integer minus integer will always be an integer.

Is my explanation and thinking correct to arrive at answer C?
[Reveal] Spoiler: OA

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E.

MGMAT 1 --> 530
MGMAT 2--> 640
MGMAT 3 ---> 610
GMAT ==> 730

Kudos [?]: 4121 [0], given: 217

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Joined: 02 Sep 2009
Posts: 41892

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Re: If P is an integer then Q an integer as well? [#permalink]

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11 Feb 2012, 18:50
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If p is an integer, is q an integer?

(1) The average (arithmetic mean) of p, q, and r is p --> p+q+r=3p --> q+r=2p --> since p is an integer then 2p is an integer --> q+r=integer. Now, if r=integer then q=integer too but if r is not an integer then q also won't be an integer. Not sufficient.

(2) r is an integer. Clearly insufficient.

(1)+(2) From (2) r=integer thus from (1) q=integer. Sufficient.

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Re: If p is an integer, is q an integer? [#permalink]

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27 Jun 2015, 16:09
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Re: If p is an integer, is q an integer?   [#permalink] 27 Jun 2015, 16:09
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