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05 Apr 2019, 08:20
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A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
25%
(medium)
Question Stats:
71% (01:02) correct
29%
(01:02)
wrong
based on 174
sessions
History
Date
Time
Result
Not Attempted Yet
If x is a positive integer, what is x?
(1) x^2 + 7x – 18 = 0
(2) x^2 – 7x + 10 = 0
(1) x^2 + 7x – 18 = 0
(2) x^2 – 7x + 10 = 0
05 Apr 2019, 08:22
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dabaobao
The Crucial Info Trap – The Devil is in the Details
Courtesy: Manhattan Prep (https://gmatclub.com/forum/4-common-typ ... 94680.html)If the GMAT tells you a piece of information, there’s usually a reason for it. But all too often, students will spend all their time doing the math and completely forget a crucial statement that the GMAT gave.
Besides being a 1 looks like 2 trap, this question has a crucial piece of information hidden at the beginning that leads to a lot of wrong answer choices: x is positive. Statement 1 tells us x could be -9 or 2, but because x must be positive, we know what x must be. Statement 2 tells us x could be 2 or 5, but both of these values are positive. The correct answer is A.
Takeaway
As you read a question, write any important information down on paper so you don’t forget them once you dive into the computations.
05 Apr 2019, 09:47
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dabaobao
Given: x is a positive integer
Target question: What is the value of x?
Statement 1: x² + 7x – 18 = 0
Factor: (x + 9)(x - 2) = 0
So, EITHER x = -9 OR x = 2
Since we're told x is POSITIVE, we can rule out x = -9
So, the answer to the target question is x = 2
Since we can answer the target question with certainty, statement 1 is SUFFICIENT
Statement 2: x² – 7x + 10 = 0
Factor: (x - 5)(x - 2) = 0
So, EITHER x = 5 OR x = 2
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT
Answer: A
Cheers,
Brent
