DS Sequence.

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rakeshd347: Master | Next Rank: 500 Posts; Posts: 391; Joined: Sat Mar 02, 2013 5:13 amFollowed by: 4 members; Thanked: 50 times

by rakeshd347 » Fri Oct 04, 2013 11:30 pm

Is the product of all of the elements in Set S negative?

(1) All of the elements in Set S are negative.
(2) There are 5 negative numbers in Set S.

OA soon.

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Source: Beat The GMAT — Data Sufficiency | Fri Oct 04, 2013 11:30 pm

theCodeToGMAT: Legendary Member; Posts: 1556; Joined: Tue Aug 14, 2012 11:18 pmFollowed by: 34 members; Thanked: 448 times; GMAT Score:650

by theCodeToGMAT » Fri Oct 04, 2013 11:37 pm

TO find --> Product Negative.
# Even number of -ve numbers or
# is "0" present in set

Statement 1:
All elements negative doesn't tell us whether -ve are in "even" number
INSUFFICIENT

Statement 2:
5 negative Number doesn't clear out the ambiguousy of "0"
INSUFFICIENT

Combining..
there is no ZERO.
SUFFICIENT

Is the Answer {C}???

R A H U L

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vinay1983: Legendary Member; Posts: 643; Joined: Wed Aug 14, 2013 4:27 amFollowed by: 7 members; Thanked: 48 times

by vinay1983 » Sat Oct 05, 2013 1:18 am

rakeshd347 wrote:Is the product of all of the elements in Set S negative?

(1) All of the elements in Set S are negative.
(2) There are 5 negative numbers in Set S.

OA soon.

This has to be C

You can, for example never foretell what any one man will do, but you can say with precision what an average number will be up to!

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GMATGuruNY: GMAT Instructor; Posts: 15539; Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members; Location: New York, NY; Thanked: 13060 times; GMAT Score:790

by GMATGuruNY » Sat Oct 05, 2013 3:57 am

rakeshd347 wrote:Is the product of all of the elements in Set S negative?

(1) All of the elements in Set S are negative.
(2) There are 5 negative numbers in Set S.

Statement 1:
Case 1: S = {-2, -1}
Here, the product = (-2)(-1) = 2, which is POSITIVE.

Case 2: S = {-3, -2, -1}
Here, the product = (-3)(-2)(-1) = -6, which is NEGATIVE.
INSUFFICIENT.

Statement 2:
Case 1: S = {-5, -4, -3, -2, -1}
Here, the product = (-5)(-4)(-3)(-2)(-1) = -120, which is NEGATIVE.

Case 2: S = {-5, -4, -3, -2, -1, 0}
Here, the product = (-5)(-4)(-3)(-2)(-1)(0) = 0, which is NONNEGATIVE.
INSUFFICIENT.

Statements combined:
Here, the ONLY elements in Set S are 5 negative numbers.
Thus, the product = (-)(-)(-)(-)(-) = NEGATIVE.
SUFFICIENT.

The correct answer is C.

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