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please help

by AJWILL » Sat Aug 04, 2012 12:07 pm
Is the integer K odd?
(1) 7K is an odd integer.
(2) K/7 is an not an odd integer.


OA A

[spoiler]but i am unable to prove B insufficient.
looking at the statement like this-
k not equal to odd I(7)* odd I
therefore k not equal to odd integer..[/spoiler]
where m i going wrong??
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by eagleeye » Sat Aug 04, 2012 12:15 pm
AJWILL wrote:Is the integer K odd?
(1) 7K is an odd integer.
(2) K/7 is an not an odd integer.


OA A

[spoiler]but i am unable to prove B insufficient.
looking at the statement like this-
k not equal to odd I(7)* odd I
therefore k not equal to odd integer..[/spoiler]
where m i going wrong??
For statement 2:
If k=2, 2/7 is not an odd integer.
If k=3, 3/7 is not an odd integer.

The key is recognizing that to prove insufficiency we can either prove that:
1. k/7is odd /even all the time, OR
2. k/7 is not an integer.

In this case, we've used 2.
Hence B is insufficient :)
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by truplayer256 » Sat Aug 04, 2012 6:09 pm
Looking at statement 1:

Note that 7 times any odd integer always produces an odd integer, so therefore K must be odd.

Looking at statement 2:

In this case, if K/7 is not odd, then K will always be an even integer.

Only statement 1 is sufficient.
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by Anurag@Gurome » Sat Aug 04, 2012 8:23 pm
AJWILL wrote:Is the integer K odd?
(1) 7K is an odd integer.
(2) K/7 is an not an odd integer.


OA A

[spoiler]but i am unable to prove B insufficient.
looking at the statement like this-
k not equal to odd I(7)* odd I
therefore k not equal to odd integer..[/spoiler]
where m i going wrong??

(1) 7K is an odd integer.
If K = Odd, say 1, 3, 5,... then 7K will always be an odd integer.
If K = even, say 2, 4, 6,... then 7K will always be an even integer.
So, clearly K is an odd integer; SUFFICIENT.

(2) K/7 is an not an odd integer.
If K = 1, then K/7 = 1/7, which is not an odd integer but K is an odd integer here.
If K = 14, then K/7 = 14/7 = 2, which is not an odd integer, and K is an even integer.
No definite answer; NOT sufficient.

The correct answer is A.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
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