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01 May 2015, 06:32
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C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
55%
(hard)
Question Stats:
60% (01:38) correct
40%
(01:41)
wrong
based on 216
sessions
History
Date
Time
Result
Not Attempted Yet
What is the value of x?
(1) \(x^2+x+10=16\)
(2) \(x=4y^4+2y^2+2\)
Could an Expert please help with the difficulty level as well? I'm not sure if this falls in 600-700.
(1) \(x^2+x+10=16\)
(2) \(x=4y^4+2y^2+2\)
Could an Expert please help with the difficulty level as well? I'm not sure if this falls in 600-700.
01 May 2015, 07:23
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Shalabh09
What is the value of x?
(1) \(x^2+x+10=16\) --> \(x^2+x-6=0\) --> x=-3 or x=2. Not sufficient.
(2) \(x=4y^4+2y^2+2\). Without knowing the value of y we cannot get the value of x. Not sufficient.
Notice that from this statement it follows that x must be positive: \(x=4y^4+2y^2+2=(nonnegative)+(nonnegative)+(positive)=positive\).
(1)+(2) Since from (2) x is positive, then from (1) we are left with x=2. Sufficient.
Answer: C.
P.S. As for the difficulty level, I'd say it's ~550-600 level question.
01 May 2015, 15:09
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Hi Shalabh09,
The GMAT often finds ways to test you on concepts that you know, but in ways that you're not used to thinking about. This question isn't too difficult (I'd rank it in the low-600s), but it does test you on Quadratics in ways that you're probably not used to thinking about.
Bunuel's explanation showcases the necessary "math" involved, so I won't rehash any of that here. Instead, I'll talk about the 'patterns' that you're supposed to spot in the construction of this question.
First, we're asked for the value of X. This is a standard question to ask in DS.
Second, Fact 1 gives us what appears to be a Quadratic equation with some extra "math" thrown in. You're probably used to solving Quadratic equations when they are set equal to 0..... so do the necessary math to set THIS equation equal to 0 and solve. You'll find that there are 2 solutions: X = -3 and X = 2. Fact 1 is INSUFFICIENT
Third, Fact 2 shows us that X is based on the value of Y. Since Y could be ANY value, there are multiple values for X. Fact 2 is INSUFFICIENT. There IS another thing worth noting about Fact 2 though...Notice the "even powers".....no matter what value you plug in for Y, the value of X will ALWAYS be POSITIVE.....
Combined, we know.....
X = -3 or X = 2
X will ALWAYS be positive
Combined, SUFFICIENT
Final Answer:
GMAT assassins aren't born, they're made,
Rich
The GMAT often finds ways to test you on concepts that you know, but in ways that you're not used to thinking about. This question isn't too difficult (I'd rank it in the low-600s), but it does test you on Quadratics in ways that you're probably not used to thinking about.
Bunuel's explanation showcases the necessary "math" involved, so I won't rehash any of that here. Instead, I'll talk about the 'patterns' that you're supposed to spot in the construction of this question.
First, we're asked for the value of X. This is a standard question to ask in DS.
Second, Fact 1 gives us what appears to be a Quadratic equation with some extra "math" thrown in. You're probably used to solving Quadratic equations when they are set equal to 0..... so do the necessary math to set THIS equation equal to 0 and solve. You'll find that there are 2 solutions: X = -3 and X = 2. Fact 1 is INSUFFICIENT
Third, Fact 2 shows us that X is based on the value of Y. Since Y could be ANY value, there are multiple values for X. Fact 2 is INSUFFICIENT. There IS another thing worth noting about Fact 2 though...Notice the "even powers".....no matter what value you plug in for Y, the value of X will ALWAYS be POSITIVE.....
Combined, we know.....
X = -3 or X = 2
X will ALWAYS be positive
Combined, SUFFICIENT
Final Answer:
GMAT assassins aren't born, they're made,
Rich
