does z = 8? (1) z = 2 or z = 8 (2) z = 3 or z = 8 e (1) z =

Question

does z = 8?

(1) z = 2 or z = 8
(2) z = 3 or z = 8

e

(1) z = 2 or z = 8
(2) z = 8

b

(1) z = 3 or z = 6
(2) z = 8

d

(1) z = 9 or z = 3
(2) z = 9 or z = 8

a

I'm trying to understand the answer format. Is it appropriate to AND 1 and 2 when neither is sufficient alone? Thanks for feedback.

risingstar · Answer

does z = 8?

(1) z = 2 or z = 8
(2) z = 3 or z = 8

it should be c, both together are sufficient?

srini123 · Answer

I still think the answer is E.

because when we combine we are saying each statement is true and it means z=8 or z=2 or z= 3, we still cannot say if z=8 or not, in once case it is =8 and in 2 others its not. hence E

Bunuel · Answer

The questions below are Yes/No type of DS problems. If you are able to answer the q yes or no, with the help of either of statement or both, it's sufficient.
 
Does z = 8?

(1) z = 2 or z = 8
(2) z = 3 or z = 8

Answer: C (z=8): from (1) you have that z is either 2 or 8; from (2) either 3 or 8. Intersection of these statements gives unique value for z, which is 8. When the answer is C it means that two statements together are sufficient to determine the answer.

(1) z = 2 or z = 8
(2) z = 8

Answer: B. (z=8)

(1) z = 3 or z = 6
(2) z = 8

Answer: D?. This type of question WILL NEVER OCCUR in real GMAT test. Remember in DS statements (1) and (2) NEVER contradict. Here (2) gives us the unique value for z, BUT (1) says that z=2 or z=6, they clearly contradict: from (1) you get that z is not equal to 8, and from (2) you get that z equals to 8.

Difference with the first question (answer C) is following: in that case our answer z=8 doesn't contradict with either of statements, (1) is saying that z is either 2 or 8 and (2) either 3 or 8. So, our answer z=8 doesn't contradict.

(1) z = 9 or z = 3
(2) z = 9 or z = 8

Answer: A (z doesn't equal to 8)

srini123 · Answer

Does z = 8?

(1) z = 2 or z = 8
(2) z = 3 or z = 8

Answer: C (z=8): from (1) you have that z is either 2 or 8; from (2) either 3 or 8. Intersection of these statements gives unique value for z, which is 8. When the answer is C it means that two statements together are sufficient to determine the answer.

Bunuel, I think answer is E

because even when we consider S1 and S2, all we know is z=2 or 3 or 8, not a single value of 8 for sure.
Why do we consider intersecting the S1 and S2 ? we do union all the time (that is take information from both).

I think this cannot be a GMAT question, if it is, the answer has to be E. please elaborate why intersection, why not union - thanks

eresh · Answer

I believe the 2nd and fourth answer is clear. As already said, the 3rd is contradictory.

For the first one, I believe it should be C.

Think of these as the equation of two straight lines. The first one is (z-2)(z-8)=0 (or z^2-10z-24=0) and the second one is (z-3)(z-8)=0 (or z^2-11z-24=0), individually these are insufficient but together there is only one common point 8, hence the answer is C.

IanStewart · Answer

It is certainly not a very GMAT-like question, but the answer is certainly C. From Statement 1, we know that z is either 2 or 8. Could z be 2? Well, from Statement 2, we know z is either 3 or 8. So clearly z is not 2. That only leaves one value for z -- 8.

srini123 · Answer

Thanks for the explanation. I'll use this logic when I combine S1 and S2 for my GMAT.

risingstar · Answer

I got them from a Kaplan book. I didn't know why they used them, but now I understand they simply illustrate how ds answer choices should be construed.

That is, if neither stmt 1 or 2 alone can be used to answer the question, see if their intersection can give a sufficient answer.

does z = 8? (1) z = 2 or z = 8 (2) z = 3 or z = 8 e (1) z =

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