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Is y = 6 ?

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Is y = 6 ?

by BTGmoderatorDC » Thu Oct 12, 2017 6:18 am
Is y = 6 ?

$$\left(1\right)\ y^2\ =\ 36$$

$$\left(2\right)\ y^2\ -\ 7y\ +\ 6\ =\ 0$$

How would i determine which of the statement is the correct Option? Can some experts help me with this?

OA C
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Source: — Data Sufficiency |

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by Brent@GMATPrepNow » Thu Oct 12, 2017 6:26 am
lheiannie07 wrote:Is y = 6 ?

$$\left(1\right)\ y^2\ =\ 36$$

$$\left(2\right)\ y^2\ -\ 7y\ +\ 6\ =\ 0$$
Target question: Is y = 6 ?

Statement 1: y² = 36
If y² = 36, then EITHER y = 6 OR y = -6
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: y² - 7y + 6 = 0
Factor the equation to get: (y - 1)(y - 6) = 0
So, EITHER y - 1 = 0 OR y - 6 = 0
So, EITHER y = 1 OR y = 6
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
Statement 1 tells us that EITHER y = 6 OR y = -6
Statement 2 tells us that y = 1 OR y = 6
Since BOTH statements are TRUE, we can conclude that y = 6
Since we can answer the target question with certainty, the combined statements are SUFFICIENT

Answer: C

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by Matt@VeritasPrep » Fri Oct 13, 2017 11:45 am
S1:

y² - 36 = 0

(y + 6) * (y - 6) = 0

y = 6 or y = -6

S2:

(y - 1) * (y - 6) = 0

y = 1 or y = 6

S1 + S2:

Only y = 6 fits both!
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