If a^3b^4c^5

Question

If  a^3b^4c^5 < 0 , is  abc < 0 ?

(1) a < 0
(2) b > 0

GMATinsight · Answer

Question: is abc < 0? Given: a^3b^4c^5 < 0 Since, b^4 is always non-negative therefore we learn that ac < 0 i.e. a and c have opposite signs i.e. we need only the sign of b and abc will be less than zero when b is positive hence Question REPHASED: is b > 0? Statement 1 : a < 0 NOT SUFFICIENT Statement 2 : b > 0 SUFFICIENT Answer: Option B

SaquibHGMATWhiz · Answer

Solution: Pre Analysis: Given a^3b^4c^5 < 0 which can also be written as a^3c^5<0 because b^4 will be positive If a^3c^5<0 then we can say that ac<0 or a and c are of opposite signs Now, abc<0 is possible only when b>0 So, the question is asking us if b > 0 or not Statement 1: a < 0 No information on b Insufficient. Eliminate options A and D Statement 2: b > 0 Clearly sufficient Hence the right answer is Option B

If a^3b^4c^5 < 0, is abc < 0? (1) a < 0 (2) b > 0

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