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Sequence S consists of 24 nonzero integers. If each term in [#permalink]
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25 Nov 2007, 05:03
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Sequence S consists of 24 nonzero integers. If each term in S after the second is the product of the 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.



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Re: DS Sequence S [#permalink]
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25 Nov 2007, 06:07
bmwhype2 wrote: Sequence S consists of 24 nonzero integers. If each term in S after the second is the product of the 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.
I'm getting B.
Stat 1: All integers could be positive or first two negative. Number of negatives will vary. Insuff.
Stat 2: Only 2 sequences are possible:
, , +, , , + or , +, , , +, 
In each case number of ve integers will be 16. Suff.



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i think its C.
A isnt sufficient because it means that either first two terms are both positive or both negative
B isnt sufficient because since 4th term is negative, could mean 2nd and 3rd terms are pos/neg, or neg/pos.
Together, we know 4th term is neg and 3rd is pos, therefore 2nd term has to be neg, and first term will be neg as well ... and fifth term will be neg and so on



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Re: DS Sequence S [#permalink]
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25 Nov 2007, 13:31
GK_Gmat wrote: bmwhype2 wrote: Sequence S consists of 24 nonzero integers. If each term in S after the second is the product of the 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. I'm getting B. Stat 1: All integers could be positive or first two negative. Number of negatives will vary. Insuff. Stat 2: Only 2 sequences are possible: , , +, , , + or , +, , , +,  In each case number of ve integers will be 16. Suff.
I agree on B. either way (3 positive or 3 negative) result is 16 negatives. GKMat, how did you come up with the 16 negative total?



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Sequence S consists of 24 nonzero integers. If each term in S after the second is the product of the 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.
from one
the first 2 intigers are either +ve or both ve
(,,+,,,+,,,+...24th ) 16 ve
(+,+,+...24th) ..0 ve insuff
from 2
(,,+,,,+.24th) 16ve
(,+,,,+,,+,,,+,,,+..24th)16ve( every 3 intigers 2 r ve)
my answer is B
from 1 insuff



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Re: DS Sequence S [#permalink]
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26 Nov 2007, 04:31
asdert wrote: GK_Gmat wrote: bmwhype2 wrote: Sequence S consists of 24 nonzero integers. If each term in S after the second is the product of the 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. I'm getting B. Stat 1: All integers could be positive or first two negative. Number of negatives will vary. Insuff. Stat 2: Only 2 sequences are possible: , , +, , , + or , +, , , +, In each case number of ve integers will be 16. Suff. I agree on B. either way (3 positive or 3 negative) result is 16 negatives. GKMat, how did you come up with the 16 negative total?
If you see the boldfaced above, the pattern contains 6 integers and 4 negatives in each case. Since there are a total of 24 integers, there will be 4 such patterns of 6 integers in which 4 negatives are repeated each time. Therefore, total number of negatives will be 4*4=16.










