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Is ? A^7 b^2c^3> 0 1.BC<0 2. AC>0 Explanation

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Senior Manager
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Is ? A^7 b^2c^3> 0 1.BC<0 2. AC>0 Explanation [#permalink]

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New post 20 Jul 2009, 10:15
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A
B
C
D
E

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Is ?
A^7 b^2c^3> 0
1.BC<0
2. AC>0

Explanation given:

Statement (1) by itself is insufficient. Consider A=1,B=1 ,C=-1 (the answer is "no") and A=1,B=-1 ,C=1 (the answer is "yes").

Statement (2) by itself is insufficient. If B is 0, the answer is "no".

Statements (1) and (2) combined are sufficient. From S1 it follows that B is not 0. Now S2 is sufficient to answer "yes".

The correct answer is C.

I have a doubt here.

By statement 2 if B is 0 it can not be <0, what ever be the value of C. Hence ans can not be C but B. Can somebody please explain.

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Re: GMat club test M11 doubt [#permalink]

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New post 20 Jul 2009, 11:19
Its a deliberate trap and I too fell in it :)

Is \(A^7 b^2c^3> 0\)
1.BC<0
2. AC>0

when AC > 0 , there is nothing mentioned about B. its just that A and C are either both positive or
both negative.

1 gives that missing piece of info that B is either positive or negative but not 0 and this is crucial piece.

Thats where DS gets tricky.

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Re: GMat club test M11 doubt [#permalink]

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New post 20 Jul 2009, 13:08
[quote="vaivish1723"]Is ?
A^7 b^2c^3> 0
1.BC<0
2. AC>0


for the expression to be>0 both A,C have to have the same sign and b not = 0 ( ie: we ve 2 conditions to satisfy)

from one

b,c ve different signs, b is not 0.......insuff

from 2

AC both have the same sign no info about b......insuff

both we have the 2 conditions satisfied..suff

C

Kudos [?]: 418 [0], given: 49

Re: GMat club test M11 doubt   [#permalink] 20 Jul 2009, 13:08
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Is ? A^7 b^2c^3> 0 1.BC<0 2. AC>0 Explanation

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