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set of numbers

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by mehrasa » Sun Sep 11, 2011 5:21 am
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
(Al I only
(B) IIonly
(C) I and II only
(D) II and III only
(E) I, II , and III

the OA is D
while I think I can be also true because the Q did not mention that -1 is the first member of set but one member of the set, so we can have -5 in the set as well and under this circumstance, we can also have -3.. to me the answer is
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by shankar.ashwin » Sun Sep 11, 2011 6:20 am
I agree what you said is correct. But since the question asks us which of the following MUST also be, you could ignore -3 because you do not know for sure where the set begins, so there is a chance of -3 not being there too.

That said, the set could possibly contain only 2 numbers say (-1,1) and in that case even 5 would not be a certain element. Dont think the problem is very clear here.
mehrasa 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
(Al I only
(B) IIonly
(C) I and II only
(D) II and III only
(E) I, II , and III

the OA is D
while I think I can be also true because the Q did not mention that -1 is the first member of set but one member of the set, so we can have -5 in the set as well and under this circumstance, we can also have -3.. to me the answer is
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Join the discussion