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DS - Help!!!

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DS - Help!!!

by agemroy » Mon Jul 07, 2008 8:28 am
What is the sum of a certain pair of consecutive odd integers?
(1) At least one of the integers is negative.
(2) At least one of the integers is positive.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.


OA is C. Plz explain.
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by wilderness » Mon Jul 07, 2008 12:27 pm
Pretty straight forward.

1) many different pairs of consecutive odd numbers are possible. The only condition is that one of them should be negative. Pairs -100001, 100003 and -1, -3 as well as -1,1 will all satisfy this condition.

2) similar situation, only sign changed. Here 1 number has to be positive.

TOGETHER: The only pair that fulfils the condition is -1,1 whose sum is 0.

So D is correct.
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by gmatinjuly » Mon Jul 07, 2008 2:55 pm
wilderness think u meant c is answer...

Here is my soltion.

1. 3 number : atleast one is negative...
so numbers can be -1,-2 0
-1 0 1
-3 -2 -1
-100 -99 -98
all satisy atlease one -ve

2. atleast one positive again -1 0 1
1 2 3
0 1 2

now both conditions
one number needs to be +ve
one number needs to be -ve
and they all are consecutive
only soln is -1 0 1 ....abd their sum u can determine....

So C is answer.
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