Both n and n+1 are in a set. Is 100 in the set? 1) 50 is in

Question

Both n and n+1 are in a set. Is 100 in the set?
1) 50 is in the set.
2) 150 is I the set

twixt · Answer

Is this question an official one ?
It is not crystal clear if the set only includes n and n+1 then answer is D or is not restricted to this two numbers then answer is E ...

lovely_baby · Answer

The answer is A
1) If 50 in the set then 51 in the set then 52 in the set... till 100 Suff
2) If 100 in the set that doesn't me 99 isi n the set Insuff

twixt · Answer

If u r right lovely, this stem wording is awful !

twixt · Answer

If n and n+1 are in the set whatever n is, then this set is infinite and the answer should be D as we just need to know that at least one integer is in the set to be sure all integers are...
I am quite puzzled with this one...

lovely_baby · Answer

Sure this set is infinite
But! if 150 is in the set then in this condition you know for sure that the set is like {150,151,...}. It doesn't at all mean that 100 in the set. That is why 2) Insuff

vprabhala · Answer

it says if N then N+1
doesn't say the other way around if N+1 so N.. thats why just A..

twixt · Answer

It just says "Both n and n+1 are in a set"

Sorry for being painful but it does NOT mean obviously that the set starts from n to infinite values.

Where is this one from ?

lovely_baby · Answer

You are right! :-D

We don't know the number the set starts with That is why 2) Insuff But we know that if N in the set then N+1 in the set too thats why 1) Suff

DLMD · Answer

Lovely_baby & Vprabhala

Thanks for the clarification, I was going to choose A but feel so uncertain. 

Twixt, this one is from real gmat test, it might give you a taste about what gmat Q look like now since OG is kind outdated, especially on Q.

banerjeea_98 · Answer

D for me. I agree with Twixt, we can't assume that the set runs to infinity.

Statement 1 : If 50 is in the set that means 50 is either n+1 or n, so we can have sets of 49, 50 or 50, 51...so ans is No...suff

Statement 2: If 150 is in the set that means 150 is either n+1 or n, so we can have sets of 149, 150 or 150, 151...so ans is No...suff

DLMD · Answer

Banerjeea:

the sequence is going upward, not downward

btw, the OA is A

greenandwise · Answer

A. If 50 is in the set then 51 is in the set, if 51 is in the set then 52 is in the set..and so on and so forth until you get to 100. The second statement is insufficient because you don't know the range of the set.

banerjeea_98 · Answer

hmmm....You said this is a real GMAT ques....how did u get the OA ? I still don't agree that there is any sequence here....just my thought...may be I am wrong but I wud still go with D per my analysis :-D

greenandwise · Answer

Actually I change my answer to E after looking at all of your responses. The fact is there are a couple of things we do not know.

1) Is the set finite or infinite...if the set is infinite then D is the answer but this is never specified in the question

2) when they give a integer which is in the set is that integer n or is it n+1 or is it both. If it is both then it gets back to my question of whether or not the set is infinite or finite.

Because we don't know this I come to E.

pb_india · Answer

My pick is "A"
I don;t see what't the confusion here.. the quesion is as clear as crystal.

A.) if 50 is in set, so is 51,52,53,.....100 So Suff

B) if 150 is in set, 151,152,....are for sure in set...but we cannot say whether 100 is as we don;t know whether 149 is in the set.

If A then B, if B is true, we cannot say anything about A
If 149 then 150, 150 is true, does not mean there is 149

Both n and n+1 are in a set. Is 100 in the set? 1) 50 is in

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