please help me to understand the answer for this question:
1.What is the value of |x| ?
A) X=- |x|
B)X SQR=4
The answer is B
My answer is A
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Question 1 OG :2015 :DS
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Brent@GMATPrepNow
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I believe the question should be worded as follows:
Statement 1: x = -|x|
This statement doesn't FEEL sufficient, so I'm going to TEST some values.
There are several values of x satisfy statement 1. Here are two:
Case a: x = 0, (since 0 = -|0|). In this case, |x| = |0| = 0
Case b: x = -1, (since -1 = -|1|). In this case, |x| = |-1| = 1
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT
Aside: For more on this idea of plugging in values when a statement doesn't feel sufficient, you can read my article: https://www.gmatprepnow.com/articles/dat ... lug-values
Statement 2: x² = 4
There are two solutions to this equation: x = -2 and x = 2
However, this does not mean that the statement is insufficient, because the question is not asking us to find the value of x. We're asked to find the value of |x|, and in both cases, we get the SAME ANSWER
Case a: x = -2. In this case, |x| = |-2| = 2
Case b: x = 2. In this case, |x| = |2| = 2
So, we can be CERTAIN that |x| = 2
Since we can answer the target question with certainty, statement 2 is SUFFICIENT
Answer = B
Cheers,
Brent
Target question: What is the value of |x|?Sh_QR wrote: 1.What is the value of |x| ?
A) x = -|x|
B) x² = 4
Statement 1: x = -|x|
This statement doesn't FEEL sufficient, so I'm going to TEST some values.
There are several values of x satisfy statement 1. Here are two:
Case a: x = 0, (since 0 = -|0|). In this case, |x| = |0| = 0
Case b: x = -1, (since -1 = -|1|). In this case, |x| = |-1| = 1
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT
Aside: For more on this idea of plugging in values when a statement doesn't feel sufficient, you can read my article: https://www.gmatprepnow.com/articles/dat ... lug-values
Statement 2: x² = 4
There are two solutions to this equation: x = -2 and x = 2
However, this does not mean that the statement is insufficient, because the question is not asking us to find the value of x. We're asked to find the value of |x|, and in both cases, we get the SAME ANSWER
Case a: x = -2. In this case, |x| = |-2| = 2
Case b: x = 2. In this case, |x| = |2| = 2
So, we can be CERTAIN that |x| = 2
Since we can answer the target question with certainty, statement 2 is SUFFICIENT
Answer = B
Cheers,
Brent
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Max@Math Revolution
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Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and equations ensures a solution.
1.What is the value of |x| ?
1) X=- |x|
2) X^2=4
According to the variable approach method, there is 1 variable (x) in the original condition and we need 1 equation to match the number of variables and equations. Since we 1 each in 1) and 2), D is likely the answer.
In case of 1), x<0 therefore it is not unique. Thus the condition is NOT sufficient
In case of 2), x=-2,2==> |x|=|-2|,|2|, x=2 the answer is unique, therefore it is sufficient
The answer is B.
If you know our own innovative logics to find the answer, you don't need to actually solve the problem.
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1.What is the value of |x| ?
1) X=- |x|
2) X^2=4
According to the variable approach method, there is 1 variable (x) in the original condition and we need 1 equation to match the number of variables and equations. Since we 1 each in 1) and 2), D is likely the answer.
In case of 1), x<0 therefore it is not unique. Thus the condition is NOT sufficient
In case of 2), x=-2,2==> |x|=|-2|,|2|, x=2 the answer is unique, therefore it is sufficient
The answer is B.
If you know our own innovative logics to find the answer, you don't need to actually solve the problem.
www.mathrevolution.com
- The one-and-only World's First Variable Approach for DS and IVY Approach for PS that allow anyone to easily solve GMAT math questions.
- The easy-to-use solutions. Math skills are totally irrelevant. Forget conventional ways of solving math questions.
- The most effective time management for GMAT math to date allowing you to solve 37 questions with 10 minutes to spare
- Hitting a score of 45 is very easy and points and 49-51 is also doable.
- Unlimited Access to over 120 free video lessons at https://www.mathrevolution.com/gmat/lesson
- Our advertising video at https://www.youtube.com/watch?v=R_Fki3_2vO8
