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What is the value of y?

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What is the value of y?

by M7MBA » Fri Apr 20, 2018 2:27 am

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What is the value of y?

(1) y^2 + 8y + 16 = 0
(2) y < 0

The OA is the option A.

From the first statement, don't we get two different option for y? Why is it sufficient?
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Source: — Data Sufficiency |

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by Brent@GMATPrepNow » Fri Apr 20, 2018 5:17 am

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M7MBA wrote:What is the value of y?

(1) y² + 8y + 16 = 0
(2) y < 0
Target question: What is the value of y?

Statement 1: y² + 8y + 16 = 0
Factor to get: (y + 4)(y + 4) = 0
So, y MUST equal -4
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: y < 0
If y is NEGATIVE, then there are infinitely many possible values for y.
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Answer: A

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by [email protected] » Sat Apr 21, 2018 4:18 pm

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Hi M7MBA,

We're asked for the value of Y.

1) Y² + 8Y + 16 = 0

Fact 1 gives us a Quadratic set equal to 0, so there could only be 0, 1 or 2 possible solutions (in this type of prompt, the GMAT will not put us in a situation in which there are 0 solutions). If there is just one solution, then Fact 1 will be sufficient. If there are two DIFFERENT solutions, then Fact 1 will be insufficient....
Y² + 8Y + 16 = 0
(Y+4)(Y+4) = 0
Thus, Y= -4 is the ONLY solution.
Fact 1 is SUFFICIENT

2) Y < 0

Fact 2 tells us that Y is negative, but we still don't know the exact value of Y.
Fact 2 is INSUFFICIENT

Final Answer: A

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