^^ this is the exact rationale. This problem has 2 main components. 1) It's an infinite set always increasing by 2, and 2) You can only assume that -1 is the lowest number since it's a MUST question. Starting with -1 yields the narrowest choice, and D is thus, as egybs said, unambiguously correct.egybs wrote:Wow.. blast from the past! As I said a year and a half ago, before I scored 99th percentile on the gmat, the answer is unambiguously D. In case the old posts are enough of an explanation here it goes again:
The set is going to be infinitely long and will continue increasing positively. Any number that's in the set will also have the same number + 2 (t+2). So if we know that 4 is in the set, 6, 8, 10,12, 14, 16, 18,20, etc, etc, etc are also definitely there.
So if we know that -1 is in the set, we know with certainty that 1,3,5,7,etc are also in the set.
What we don't know is where the trend starts. -1 could be the lowest number, but it could also be -3, or -5, or even -4.. we just don't know where it starts. Therefore, the only thing we can conclude with certainty is that -1,1,3,5,7,9, etc are in the set. So the answer is, once again, unambiguously, D.
GMATBootcamp
Starts Sep 28
LIVE ONLINE BOOTCAMP
Live Online Bootcamp Class with Top GMAT Expert Chris Peckover
15 live classes from Sep 28, 2026
- Schedule
- Mon to Fri · 7:00 to 10:00 PM ET
- Included
- Live classes + 6 months of TTP OnDemand
- Boost your GMAT score in less than one month in a live online class
- 6 months access to TTP OnDemand video courses included
View bootcamp & enroll
Limited cohort · enrollment open
