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Sequence S consists of 24 nonzero integers. If each term in [#permalink]
 07 Feb 2004, 13:25
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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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Manager
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E. Let S = {x, y, xy, a, b, ab,....................}
Statement 1: Not enough as irrespective of first 2 terms, the third term will be always positive.
Statement 2: Not enough as there can be n number of negatives
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SVP
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you misunderstood the question.
The set has following numbers
{x,y, xy, xy^2, xy^3, xy^4, xy^5 .... }
Please try again.
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Manager
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 then is it C as we can get both x & y as negatives.
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SVP
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Hi rakesh,
I did a mistake again. Here is the series.
{ x, y, xy, xy^2, x^2 y^3, x^3 y^5 ... }
Please try again.
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Intern
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{ x, y, xy, xy^2, x^2 y^3, x^3 y^5 ... }
(1) The third term in S is positive. => X and Y are both positive or both negative.
(2) The fourth term in S is negative.=> xy^2 is negative => x is negative... but we cannot conclude whether y is negative or positive...
From (1) and (2) we can conclude that x=negative and y=negative...
Answer is C.
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Manager
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Anand! in any case the 3rd and the 4th terms wont change. So I stand by C.
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Director
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My Answer is C.
How many of the series are negative is the question?
Given that number starting from 3rd is muliple of previous two numbers.
From (1) third is positive. That means, 1nd and 2nd are both either positive or negative.
NOT SUFF
From (2) 4 is negative. 3rd and 4th either one is negative and the other
is positive. NOT SUFF
To gather.
3rd is postive ; 2nd should be negative and so is the first.
Provided information is enough to find number of negative numbers in the set.
Last edited by kpadma on 08 Feb 2004, 19:51, edited 1 time in total.
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Intern
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I think the answer is B as the statement II reveals that x is negative. Now irrespective of the sign of y (positive or negative), the no. of negative terms in the sequence is 16.
Anand, please confirm.
N.B.: I am new and so if I have violated any ettiquette I am sorry.
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SVP
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hi aimps,
Please dont hesitate to contribute. Are u mislead by my status as major shareholder. This is just a promotion I get for posting many times. I am sure you will also achieve that by contributing more.
Welcome to the club.
Yes u r right the answer is B.
Hi kpadma and rakesh,
You have been good. Please respect every question. Dont pounce on them I am suprised that u got this wrong. Work it boys. I do these mistakes many times and pay for them.
Here is the hint. Dont have to do for 24 numbers. Just take 6 numbers
x, y, xy, x*y^2, x^2 * y^3, x^3*y^5
Make a table and try the problem again.
Be careful about the answer C. May times they create problems containing two variables. Choice A and B will have equation which will lead you to believe that combining both of them will get you the answer. I get 4-5 problems wrong like this on kaplan. Just act a little dumb and go through each choice completely. It is worth it.
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Manager
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Thanks Anand! Now I know why i get many problems wrong in DS.
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close
