Is y = 7?

Question

Is y = 7?

(1) (x - 3) = 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

Skywalker18 · Answer

(1) (x - 3) = 0
=> x =3
We have no information about value of y
Not sufficient
(2) (x - 3)(y - 7) = 0
=> x=3 or y = 7
Not sufficient
Combining 1 and 2 , we get
Not sufficient as y may or may not be equal to 7
Answer E

cutegirlsimran · Answer

Sorry I noted down the question wrong first time so a new attempt

Is y = 7?

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

1) Not Sufficient as it onky gives x = 3 no value for y
2) we get x=3 and y=7
So Answer must be B as we get y=7

bigdady · Answer

Is y = 7?

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

Only statement 2, gives the exact value of y, hence Answer is B.

tallyho_88 · Answer

ans is E, although i also think it should be B. Can't seem to figure that out.

ENGRTOMBA2018 · Answer

E is the correct answer for this question.

Whenever you are given (x-a)(x-b)=0---> you can have the following 3 cases:

1. x-a = 0 and x-b  
eq  0
2. x-b = 0 and x-a  
eq  0
3. x-a = 0 and x-b = 0.

Thus, from (x - 3)(y - 7) = 0 you know that the following 3 cases are possible:

1. x-3 =0 and y-7  
eq  0
2. x-3  
eq  0 and y-7 = 0
3. x-3 = 0 and y-7 = 0.

Case 1 gives you a NO for the question asked, is y= 7 and cases 2 and 3 give you a YES for the question asked.

Thus, you get 2 different answers for the question asked. This statement, hence, is NOT sufficient.

Even when you combine the 2 statements, you eliminate case 2 above but cases 1 and 3 still stand. E is thus the correct answer.

Hope this helps.

OreoShake · Answer

Im sorry but I am unable to understand your answer. Why is that for every quadratic root, if one is equal to 0, the other is not equal to 0? I thought every quadratic had two roots thus two factors and that would be it. Could you please explain further?

Thank you.

chetan2u · Answer

Yes every quadratic equation has TWO roots.

so if (x-a)(x-b) = 0..
when can that be possible..
1)when x=a, this means one root is a, other can be anything, which can not be ascertained with the given info..
2)when x=b, this means one root is b, other can be anything, which can not be ascertained with the given info....
3)OR when BOTH x=b=0, here the roots are a and b

OreoShake · Answer

Yes every quadratic equation has TWO roots.

so if (x-a)(x-b) = 0..
when can that be possible..
1)when x=a, this means one root is a, other can be anything, which can not be ascertained with the given info..
2)when x=b, this means one root is b, other can be anything, which can not be ascertained with the given info....
3)OR when BOTH x=b=0, here the roots are a and b

Did you mean a=b=0 on the 3rd point?

So is it correct to say that - in this question, combining both AC, we only get one root of y and hence it is insufficient? (but if the question is considered 'must be true', the y=7 should be sufficient and B could be an answer)?; and if the answer choice A was (y-2)=0, then the answer to the question would have been C?

Thank you

chetan2u · Answer

Hi

the Q is JUST -   Is y=7?  --NOTHING about roots

I. tells you x=3, we do not know anything about y.. Insuff

II. tells us (x-3)(y-7)=0..
 so different cases.. 
x=3, y can be 7, 0, 1,2 .. so 7 is possible but not MUST-- 
y=7, x could be anything But suff for us..
so different CASES .. Insuff

combined we know for sure x=3, BUT y can be 7 or any other number..
so Insuff

IF statement I was y=2..
ans will be A..
since y=2, it cannot be =7..
so our answer for IS x=7? would be NO

OreoShake · Answer

Thank you Chetan

Badari · Answer

(x - 3)(y - 7) = 0 you know that the following 3 cases are possible:

1. x-3 =0 and y-7 not equal to 0
2. x-3 not equal to and y-7 = 0
3. x-3 = 0 and y-7 = 0.

Statement-1: X=3 Gives no clue of what exactly Y would be Hence Insufficient.

Statement-2: (X-3) (X-7) = 0 as discussed above Y may or may not be equal to 7.

Combining both statements still, Y may or may not be zero.

Hence E

sukeshap · Answer

it is clear x=3 in first statement
second statement says y is equal or not equal to 7, because x=3
so the answer is E

Akuthiala · Answer

Statement 1 is insufficient because it does provide any info on y
Statement 2 is insufficient because y could be anything as long a x=3

when we combine the two we get x = 3 so x-3 =0 and y could be anything

BrentGMATPrepNow · Answer

Target question :    Is y = 7?

Statement 1 : x - 3 = 0  
In other words, x = 3
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    
There are several values of x and y that satisfy BOTH statements. Here are two: 
 Case a : x = 3 and y = 7. In this case, the answer to the target question is  YES. y DOES equal 7 
 Case b : x = 3 and y = 6. In this case, the answer to the target question is  NO. y does NOT equal 7

Answer: E

Cheers,
Brent

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Is y = 7?

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