Is y = 7?
(1) x - 4 = 0
(2) (x - 3)(y - 7) = 0
[spoiler]OA=C[/spoiler].
Why is not sufficient the second statement? May someone helps me? Thanks.
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Is y = 7?
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Gmat_mission
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Vincen
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Hello Gmat_mission.
Here, we have to say if y is equal to 7 or not.
(1) x - 4 = 0
This statement implies that x=4. This doesn't give us information about y. Then it is NOT SUFFICIENT.
(2) (x - 3)(y - 7) = 0
Here we have two options: x=3 or y=7. Since y can be 7 or not, this statement is NOT SUFFICIENT.
Now, if we use both statements together we will get that necessary y=7. Therefore, here we get a unique answer. SUFFICIENT.
Hence, we have that the correct answer is the option C.
I hope it helps.
Here, we have to say if y is equal to 7 or not.
(1) x - 4 = 0
This statement implies that x=4. This doesn't give us information about y. Then it is NOT SUFFICIENT.
(2) (x - 3)(y - 7) = 0
Here we have two options: x=3 or y=7. Since y can be 7 or not, this statement is NOT SUFFICIENT.
Now, if we use both statements together we will get that necessary y=7. Therefore, here we get a unique answer. SUFFICIENT.
Hence, we have that the correct answer is the option C.
I hope it helps.
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Brent@GMATPrepNow
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Target question: Is y = 7?Gmat_mission wrote:Is y = 7?
(1) x - 4 = 0
(2) (x - 3)(y - 7) = 0
Statement 1: x - 4 = 0
In other words, x = 4
Since we have no information about y, statement 1 is NOT SUFFICIENT
Statement 2: (x - 3)(y - 7) = 0
This tells us that EITHER x = 3 OR y = 7
So, y COULD equal 7, or y might not equal 7
For example, consider these two possible cases:
Case a: x = 2 and y = 7. Notice that these values satisfy the equation (x - 3)(y - 7) = 0. In this case, the answer to the target question is YES. y DOES equal 7
Case b: x = 3 and y = 2. Notice that these values satisfy the equation (x - 3)(y - 7) = 0. In this case, the answer to the target question is NO. y does NOT equal 7
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT
Statements 1 and 2 combined
Statement 2 tells us that EITHER x = 3 OR y = 7
Statement 1 tells us that x = 4
Since statement 1 eliminates the possibility that x = 3, it MUST be the case that y = 7
In other words, the answer to the target question is YES. y DOES equal 7
Since we can answer the target question with certainty, the combined statements are SUFFICIENT
Answer: C
Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
