Does z = 3 ?

Question

Does z = 3 ?

(1) z is a solution of z^2 − 2z − 3 = 0.
(2) z is a solution of z^2 − 3z = 0

Luckisnoexcuse · Answer

(a) gives the solution of z as -1 and 3 hence insufficient

(b) gives the solution of z as 0 and 3 hence insufficient

On combining both we can answer the question
hence the answer is C

i did it wrong first time

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MvArrow · Answer

Why isn't the answer C?

Bunuel · Answer

This is an YES/NO data sufficiency question. A statement is sufficient if you can get a definite YES or definite NO answer to the question asked.

Do you have a definite YES or No answer to the question from any of the statements?

MvArrow · Answer

In both statements the equation has 2 solutions, and one of them is 3, so it could be a YES or a NOT, am I wrong?

Bunuel · Answer

Absolutely. That is why the answer is C and not D. When combined we know that z can only be 3, so we have an YES answer to the question.

ankitbokaria · Answer

There is not a definite yes or definite no in individual cases, but together we get z=3 ,which is sufficient to answer
So answer would be C

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MvArrow · Answer

Glad the my reasoning was correct

Thanks Bunuel! You guys from Gmatclub are giving me an incredible help in my preparation, and my GMAT is scheduled in two weeks :D

Luckisnoexcuse · Answer

ohh yes need a brainwash...since we have two answers from first equation and two answers from second equation...individually none of them suffice to answer the question, however when we combine them then we can say that z=3 ..hence option C

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JS1290 · Answer

Hi,

S1- z^2-2z-3=0 leads to (Z-3)(z+1) or z=3 or z=-1. Not sufficient as we have two solutions here
S2- z^2-3z=0 leads to z(z-3) or z=0 or z=3. Again not sufficient as we have again two solutions here

When we combine these, we get z=3, hence sufficient.  C

utkarshthapak · Answer

Bunuel , I think you should edit this comment as the OA has been revealed before the planned date

Bunuel · Answer

Yes, it does not make sense to hide the OA now. It's revealed now.

bettatantalo · Answer

How did you calculate this? Did you factor the two equations?

Mpuneet · Answer

1 leads to z = -1 , 3 so not sufficient

2 leads to z = 0, 3 so not sufficient

Combining, 3 is common

So z is 3

C it is.

ArjunJag1328 · Answer

Z=3?

St 1: z^2-2z-3=0
Solving it, we get z as 3 or -1  AD /BCE

St 2: z^2-3z=0
Solving it, we get z = 0 or 3  AD/B CE

Combining them, we get z=3. Hence C

Does z = 3 ?

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GMAT Data Sufficiency (DS) Questions

Does z = 3 ?

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