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# Is xy<15? 1) x<3 2) y<5

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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 6242
GMAT 1: 760 Q51 V42
GPA: 3.82
Is xy<15? 1) x<3 2) y<5  [#permalink]

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03 Oct 2017, 01:37
00:00

Difficulty:

25% (medium)

Question Stats:

77% (00:37) correct 23% (00:53) wrong based on 39 sessions

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[GMAT math practice question]

Is xy<15?

1) x<3
2) y<5

_________________

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 $99 for 3 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" PS Forum Moderator Joined: 25 Feb 2013 Posts: 1217 Location: India GPA: 3.82 Re: Is xy<15? 1) x<3 2) y<5 [#permalink] ### Show Tags 03 Oct 2017, 02:12 MathRevolution wrote: [GMAT math practice question] Is xy<15? 1) x<3 2) y<5 Statement 1: no value of $$y$$ is given. Insufficient Statement 2: no value of $$x$$ is given. Insufficient Combining 1 & 2, if $$x=2$$, $$y=4$$, then $$xy=8<15$$ but if $$x=-10$$, $$y=-2$$, then $$xy=20>15$$. Hence Insufficient Option E Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 6242 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: Is xy<15? 1) x<3 2) y<5 [#permalink] ### Show Tags 05 Oct 2017, 03:12 => Forget conventional ways of solving math questions. In DS, VA (Variable Approach) method is the easiest and quickest way to find the answer without actually solving the problem. Remember that equal number of variables and independent equations ensures a solution. There are 2 variables and 0 equation. Therefore, C is most likely to be the answer. Conditin 1) & 2) x = 1, y = 2 ➔ xy = 2 < 15 : Yes x = -4, y = -4 ➔ xy = 16 > 16 : No Therefore, unlike our expectation, E is the answer. Normally for cases where we need 2 more equations, such as original conditions with 2 variables, or 3 variables and 1 equation, or 4 variables and 2 equations, we have 1 equation each in both con 1) and con 2). Therefore, C has a high chance of being the answer, which is why we attempt to solve the question using con 1) and con 2) together. Here, there is 70% chance that C is the answer, while E has 25% chance. These two are the key questions. In case of common mistake type 3,4, the answer may be from A, B or D but there is only 5% chance. Since C is most likely to be the answer according to DS definition, we solve the question assuming C would be our answer hence using con 1) and con 2) together. (It saves us time). Obviously, there may be cases where the answer is A, B, D or E. Ans: E _________________ 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$99 for 3 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
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Re: Is xy<15? 1) x<3 2) y<5 &nbs [#permalink] 05 Oct 2017, 03:12
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# Is xy<15? 1) x<3 2) y<5

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