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Source: — Data Sufficiency |
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by this_time_i_will » Sun Sep 26, 2010 6:26 pm
imo E.

I: a+b<0. this gives many conditions. both a and b being negative, or a is positive and b is negative but |b|>|a|, or a is negative and b is psotive but |a|>|b|.

so insufficent.

II.tells nothing about b. insuffient.

I & II:
both a and b may be negative and it is not possible to know, which one.
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by thirst4edu » Sun Sep 26, 2010 6:35 pm
HPengineer wrote:Is |a| > |b|?

(1) b < -a

(2) a < 0



I am interpreting statement 1 incorrectly... Anyone willing to discuss?
Solving by picking numbers, but would like know algebraic approach for this one.

Is |a| > |b| ?

1) b < -a

if b < 0, a < 0
pick b=-2, a = -1
-2 < -(-1) --> -2<1
|a| > |b| --> |-1| > |-2| No

pick b=-5, a=-7
-5 < -(-7) --> -5 < 7
|a| > |b| --> |-7| > |-5| Yes

statement one is not sufficient

2) a < 0
For above picked numbers we have already seen that a < 0 is not sufficient.

1) & 2) Again, both statements are not sufficient for the numbers above.

so Answer IMO is E.
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by HPengineer » Sun Sep 26, 2010 9:19 pm
THe first statement is still getting me..

If B is less then a negative number doesn't that mean that B itself must be negative??

(1) b < -a
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by thirst4edu » Sun Sep 26, 2010 9:29 pm
HPengineer wrote:THe first statement is still getting me..

If B is less then a negative number doesn't that mean that B itself must be negative??

(1) b < -a
Not necessary. If b=1 and a=-2
Inequality b < -a is still true 1<-(-2) i.e. 1<2
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by HPengineer » Sun Sep 26, 2010 10:00 pm
So they are not saying A is negative but merely that there is a negative sign in front of A?

So these are the two possible scenarios for the value of A based off their statement? - (A) and -(-A)
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by hi.itz.mani » Sun Sep 26, 2010 11:16 pm
|a| >|b|

can be interpreted as

if a > 0 and b > 0 ==> a > b

if a < 0 and b > 0 ==> -a > b

if a > 0 and b < 0 ==> a > -b

if a < 0 and b < 0 ==> -a > - b

so to interpret the question we need to always know the relative value of a and b wrt 0

1 b < -a doesn't tell anything about value of b and a wrt 0 .... hence insufficient
2 a < 0 doesn't tell anything about value of b wrt 0 .... hence insufficient

joining 1 and 2 we still don't know anything about value of b hence both together also insufficient. This leaves us with E.
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