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Nova math question

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Nova math question

by hmboy17 » Sun Jun 13, 2010 9:53 pm
23. S is a set of integers such that
I) If x is in S, then -x is in S.
II) If both x and y are in S, then so is x + y.
Is -2 in S?
(1) 1 is in S.
(2) 0 is in S.
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Source: — Data Sufficiency |
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by albatross86 » Sun Jun 13, 2010 10:00 pm
We need to know if -2 is in s.

1. 1 is in S

From I) we have -1 is also in S
From II) we have 1 -1 = 0 is also in S. Insufficient.

NOTE: It might be tempting to say 1 is in S so 1+1 should also be in S based on II) but that would be adding the same number to itself, which is not mentioned in S. It only talks of 2 different members being added.

2. 0 is in S

We already knew that from I) and it didn't help us. Insufficient.

1 and 2 --> No new info. Insuff.

Pick E
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