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# Is ab > 0? (1) b*a^4 > 0 (2) b + a^3 > 0

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Director
Joined: 23 Feb 2015
Posts: 756
GMAT 1: 720 Q49 V40
Is ab > 0? (1) b*a^4 > 0 (2) b + a^3 > 0  [#permalink]

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Updated on: 08 Mar 2019, 00:35
1
00:00

Difficulty:

35% (medium)

Question Stats:

68% (01:04) correct 32% (01:50) wrong based on 25 sessions

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Is $$ab>0?$$

(1) $$b*a^4>0$$

(2) $$b+a^3>0$$

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“The heights by great men reached and kept were not attained in sudden flight but, they while their companions slept, they were toiling upwards in the night.”

Originally posted by AsadAbu on 07 Mar 2019, 11:52.
Last edited by Bunuel on 08 Mar 2019, 00:35, edited 1 time in total.
Renamed the topic and edited the question.
Math Expert
Joined: 02 Aug 2009
Posts: 7415
Re: Is ab > 0? (1) b*a^4 > 0 (2) b + a^3 > 0  [#permalink]

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07 Mar 2019, 19:21
1
Is $$ab>0?$$
so we have to find if both a and B are non zero and of same sign
1) $$b × a^4>0$$...b is surely positive, but we cannot say anything about sign of a... insufficient
2) $$b+a^3>0$$..We can just say that at least one of b or a is positive. Nothing more. Insufficient

Combined..
Insufficient

E
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1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html
4) Base while finding % increase and % decrease : https://gmatclub.com/forum/percentage-increase-decrease-what-should-be-the-denominator-287528.html

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Re: Is ab > 0? (1) b*a^4 > 0 (2) b + a^3 > 0  [#permalink]

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11 Mar 2019, 09:15
Is $$ab>0?$$

(1) $$b*a^4>0$$

(2) $$b+a^3>0$$

ab>0

#1
$$b*a^4>0$$
a can be + or -ve
insufficient
#2
$$b+a^3>0$$
a can be +ve or -ve
in sufficinet
from 1 &2
we cannto determine value whether ab>0
IMO E
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Re: Is ab > 0? (1) b*a^4 > 0 (2) b + a^3 > 0   [#permalink] 11 Mar 2019, 09:15
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