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Sequence number...

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by bpgen » Wed Jun 30, 2010 6:23 am
Sequence S consists of 24 non-zero integers. If each term in S after the second is the product of previous two terms, how many terms in S are negative?

1) The third term in S is positive

2) The fourth term in S is negative

OA B
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Source: — Data Sufficiency |

by albatross86 » Wed Jun 30, 2010 6:32 am
We don't care about the value of the integers, only the signs. Let's denote Positive as P and Negative as N.

Statement 1:

3rd term is positive.

2 possibilities:

PPP... No negatives
NNP... Definitely some negatives

INSUFFICIENT

Statement 2:

4th term is negative

Two possibilities:

NPNNPNNPNNP... You can group them as 8 groups of (NPN) (NPN) (NPN)... => 16Negatives

or NNPNNPNNPNNP.... You can group them as 8 groups of (NNP) (NNP)... -> 16 Negatives

SUFFICIENT

Pick B.
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