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# M60-24

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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 6985
GMAT 1: 760 Q51 V42
GPA: 3.82

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11 Jun 2018, 05:59
00:00

Difficulty:

45% (medium)

Question Stats:

57% (00:55) correct 43% (01:23) wrong based on 7 sessions

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If $$x$$ and $$y$$ are integers, is $$x^2+11x+13y$$ an even number?

1) $$x=11$$

2) $$y=13$$

_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
"Only $149 for 3 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 6985 GMAT 1: 760 Q51 V42 GPA: 3.82 Re M60-24 [#permalink] ### Show Tags 11 Jun 2018, 06:00 Official Solution: Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution. The first step of the VA (Variable Approach) method is to modify the original condition and the question, and then recheck the question. Now, $$x^2+11x+13y = x(x+11)+13y$$. As $$x(x+11)$$ is always an even integer (one of $$x$$ and $$x + 11$$ must be even), $$x^2+11x+13y$$ is even precisely when $$13y$$ is even. This is equivalent to $$y$$ being even, so the question can be restated as 'Is $$y$$ an even number? Condition 1) If $$x = 11$$ and $$y = 1$$, then $$x^2+11x+13y = 255$$ is an odd integer. If $$x = 11$$ and $$y = 2$$, then $$x^2+11x+13y = 268$$ is an even integer. Since the question does not have a unique answer, condition 1) is not sufficient. Condition 2) If $$y = 13$$, then $$y$$ is odd, and the answer to the question is 'no'. Condition 2) is sufficient. Therefore, B is the answer. Answer: B _________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$149 for 3 month Online Course"
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Joined: 24 Sep 2017
Posts: 1

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08 Oct 2018, 07:32
In this question, option D can also be selected as a correct answer. Since by taking values of both statements a definitive answer of the question can be obtained.
Intern
Joined: 18 Nov 2014
Posts: 12

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18 Jan 2019, 10:55
I think this is a high-quality question and I agree with explanation. different and good approach to solve the question
Re M60-24   [#permalink] 18 Jan 2019, 10:55
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# M60-24

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