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What is the value of x?

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Source: — Data Sufficiency |

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by Brent@GMATPrepNow » Thu Sep 08, 2016 1:52 pm
NandishSS wrote:What is the value of x?

1) |x| = 4
2) x² = 16
Target question: What is the value of x?

Statement 1: |x| = 4
When we solve the equation, we find that EITHER x = 4 OR x = -4
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: x² = 16
When we solve the equation, we find that EITHER x = 4 OR x = -4
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
Statement 1 told us that EITHER x = 4 OR x = -4
Statement 2 told us that EITHER x = 4 OR x = -4
So, when we COMBINE the statements, we find that told us that EITHER x = 4 OR x = -4

Since we cannot answer the target question with certainty, the combined statements are NOT SUFFICIENT

Answer = E

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by Scott@TargetTestPrep » Sun Sep 11, 2016 5:08 am
NandishSS wrote:What is the value of x?
1) |x|=4
2)x^2=16

OA:E
We need to determine the value of x.

Statement One Alone:

|x| = 4

Using the information in statement one, we know that x = 4 or x = -4, since both |4| and |-4| are equal to 4. However, since we do not have a unique value for x, statement one alone is not sufficient. Eliminate answer choices A and D.

Statement Two Alone:

x^2 = 16

Using the information in statement two, we know that x = 4 or x = -4 since both 4^2 and (-4)^2 are equal to 16. However, since we do not have a unique value for x, statement two alone is not sufficient. Eliminate answer choice B.

Statements One and Two Together:

Statements one and two provide the same information: x is either 4 or -4. Since we do not have a unique value for x, the two statements together are still not sufficient.

Answer: E

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by Matt@VeritasPrep » Fri Sep 16, 2016 2:17 pm
The key here is that DS questions asking for "the value of x" are really asking for "the one, unique value of x". If a statement tells us "x = 3 or x = 5", we do have values, but we don't have The One Unique Value that the test seeks, so that statement is insufficient.
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