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by mehrasa » Thu Sep 29, 2011 9:00 pm
sequence S consist of 24 non zero integers. if each term in S after the second is product of two previous terms. how many terms in S are negative

1) the third term in S is positive
2) the fourth term is negative


[spoiler]OA: B[/spoiler] please give ur answers with explanation
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Source: — Data Sufficiency |

by shankar.ashwin » Thu Sep 29, 2011 9:11 pm
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by Anurag@Gurome » Fri Sep 30, 2011 5:06 am
mehrasa wrote:sequence S consist of 24 non zero integers. if each term in S after the second is product of two previous terms. how many terms in S are negative

1) the third term in S is positive
2) the fourth term is negative


[spoiler]OA: B[/spoiler] please give ur answers with explanation
(1) 3rd term in S is positive implies the sequence can have all positive terms or we can have the sequence with 2 negatives and one positive term.
Since there is no definite answer; NOT sufficient.

(2) 4th term is negative implies that:
Case 1: 3rd term is positive: Then 2nd term is negative and 1st term is negative. (N, N, P, N, N,...); so 16 negative and 8 positive (as in every three terms there is 2 negative and 1 positive).

Case 2: 3rd term is negative: Then 2nd term is positive and 1st term is negative. (N, P, N, N, P,...); so 16 negative and 8 positive (as in every three terms there is 2 negative and 1 positive)

From both the cases, we get the same answer; SUFFICIENT.

The correct answer is B.
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