fiveflowers wrote:A set of numbers has the property that for any number t in the set, t + 2 is in the set. If -1 is in the set, which of the following must also be in the set?
I.-3
II.1
III.5
A I only
B II only
C I and II only
D II and III only
E I, II, and III
OA: D
If t is in the set, then t+2 is in the set.
Since
-1 is in the set, -1+2 =
1 is in the set.
Since 1 is in the set, 1+2 =
3 is in the set.
Since 3 is in the set, 3+2 =
5 is in the set..
Since the set must contain both 1 and 5 (statements II and III), eliminate A, B, and C.
If t is in the set, then t+2 is in the set.
The portion in red tells us ONLY that t+2 must be in the set.
It tells us NOTHING about values LESS than t: they could be in the set, or they could not be in the set.
Thus, given that -1 is in the set, we cannot determine whether any values LESS than -1 are in the set.
Since -3 (statement I) does not have to be in the set, eliminate E.
The correct answer is
D.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at
[email protected].
Student Review #1
Student Review #2
Student Review #3
