series S

This topic has expert replies
Senior | Next Rank: 100 Posts
Posts: 76
Joined: Sun Jul 20, 2008 10:47 am
Location: new york city
Thanked: 1 times

series S

by mberkowitz » Thu Sep 25, 2008 7:05 pm
S is a series of positive integers in which, if n is in S, n + 1 will also be in S, is 100 in S?
1) 50 is in S.
2)150 is in S.

OA A.

Senior | Next Rank: 100 Posts
Posts: 76
Joined: Sun Jul 20, 2008 10:47 am
Location: new york city
Thanked: 1 times

by mberkowitz » Thu Sep 25, 2008 7:06 pm
does this mean, if 50 is in S, than 51 is in S. and if 51 is in S, then 52 is in S. And so on until 100 and beyond?

If so, thats a crime to all well-written gmat problems.

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 2621
Joined: Mon Jun 02, 2008 3:17 am
Location: Montreal
Thanked: 1090 times
Followed by:355 members
GMAT Score:780

by Ian Stewart » Thu Sep 25, 2008 7:46 pm
mberkowitz wrote:does this mean, if 50 is in S, than 51 is in S. and if 51 is in S, then 52 is in S. And so on until 100 and beyond?

If so, thats a crime to all well-written gmat problems.
Yes, that's the intended meaning, which is why A is sufficient. B is not sufficient, because the smallest thing in the sequence might be 150 or 145 or something else which is larger than 100.

I've seen this question before on this forum, though I don't know the source. The wording above is indeed horrible, but I'm pretty sure the wording was much better the last time I saw it, so I wonder if the wording above is truly the original wording. For one thing, the question should not refer to a 'series'; it's describing either a set or a sequence. It's also a run-on sentence, so could serve double duty as an exercise in Sentence Correction.
For online GMAT math tutoring, or to buy my higher-level Quant books and problem sets, contact me at ianstewartgmat at gmail.com

ianstewartgmat.com