Is y = 7?

Question

Is y = 7?

(1) (x - 4) = 0
(2) (x - 3)(y - 7) = 0

cutegirlsimran · Answer

Is y = 7?

(1) (x - 4) = 0
(2) (x - 3)(y - 7) = 0

statement 1 gives x=4 clearly not sufficient as we dont know anything about y

statement 2 (x-3)(y-7)=0 clearly not sufficient as it gives relation in form of x and y

together 1 + 2 we get
y=7 so answer should be C

OptimusPrepJanielle · Answer

Statement 1: x = 4
Nothing is told about y. Insufficient

Statement 2:
Either x = 3 or y = 7
Still nothing can be said about y. Insufficient

Both Statements combined:
Now we know that x = 4
Hence y = 7. Sufficient. Option C

BrentGMATPrepNow · Answer

Target question :    Is y = 7?

Statement 1 : (x - 4) = 0  
This tells us that x = 4, but it provides no information about the value of y
Since we cannot answer the  target question  with certainty, statement 1 is NOT SUFFICIENT

Statement 2 : (x - 3)(y - 7) = 0 
This tells us that EITHER x = 3 OR y = 7
Consider the following cases: 
 Case a : x = 5 and y = 7. Notice that these values satisfy the equation, because we get (x - 3)(y - 7) = (5 - 3)(7 - 7) = 0. In this case, the answer to the target question is  YES, y DOES equal 7 
 Case b : x = 3 and y = 4. Notice that these values satisfy the equation, because we get (x - 3)(y - 7) = (3 - 3)(4 - 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 1 tells us that x = 4
Statement 2 tells us that EITHER x = 3 OR y = 7
If x = 4, then it CANNOT be the case that x = 3, which means  y MUST equal 7 
Since we can answer the  target question  with certainty, the combined statements are SUFFICIENT

Answer: C

Cheers,
Brent

CatchTwentyTwo · Answer

Is y = 7?

Statement 1:

If x - 4 = 0, then x = 4

This tells us nothing about the value of y, so the statement is insufficient.

Statement 2:

If (x - 3)(y - 7) = 0, then:

(a) x = 3 AND y != 7
OR 
(b) x != 3 AND y = 7
OR 
(c) x = 3 AND y = 7

Since y could be 7 or not 7, this statement is insufficient.

Statement 1+2:

We know from Statement 1 that x = 4, therefore this eliminates possibilities (a) and (c) from statement 2. Only possibility (b) is left, meaning that y = 7. This is sufficient.

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Is y = 7?

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Is y = 7?

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