NEW HERE? LEARN MORE
closeclose
Last visit was: 25 Apr 2024, 20:39 It is currently 25 Apr 2024, 20:39
Decision Tracker
My Rewards
New posts
New comers' posts

Close
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel

If b is positive, is ab positive?

SORT BY:
Date
Kudos
Tags:
Find Similar Topics 
Show Tags
Hide Tags
User avatar
L
Bunuel
Math Expert
Joined: 02 Sep 2009
Posts: 92915
Own Kudos [?]: 619044 [2]
Given Kudos: 81595
Send PM
CAT Tests Forum Quiz Mode
If b is positive, is ab positive? [#permalink] New post   11 Aug 2017, 03:43
2
Bookmarks
Expert Reply
00:00
A
B
C
D
E

Difficulty:

5% (low)

Question Stats:

88% (00:57) correct 12% (01:08) wrong based on 441 sessions
Hide Show timer Statistics
If b is positive, is ab positive?

(1) \(a^2b>0\)

(2) \(a^2+b=13\)
ShowHide Answer
Official Answer
E
User avatar
D
stonecold
Alum
Joined: 12 Aug 2015
Posts: 2282
Own Kudos [?]: 3130 [3]
Given Kudos: 893
Schools: Boston U '20 (M)
GRE 1: Q169 V154
Send PM
GMAT ToolKit User
Re: If b is positive, is ab positive? [#permalink] New post   11 Aug 2017, 04:14
3
Kudos
For ab>0 => a and b must be of the same sign.
So by giving us b>0 the question is really asking us if a>0 or not.



So the question can be transformed into -->
If b>0 then Is a>0 .

Lets begin.

Statement 1-->
a^2 * b > 0

This just tells us that a≠0
a can be positive or negative a^2*b will always be positive.

Hence not sufficient.


Statment 2->
Lets use two examples =>
(0,13)
(1,12)


Hence not sufficient.



Combining the two statements =>

(x,y) => (-1,12) or (1,12) are two easy test cases to take.

Hence not sufficient.



Hence E.
avatar
S
satsurfs
Manager
Manager
Joined: 07 Jan 2015
Posts: 51
Own Kudos [?]: 153 [1]
Given Kudos: 666
Location: United States
Schools: Ross '20 Duke '20 Sloan '20 Stern '20 Tepper '20 Tuck '20 Yale '20 Cornell Tech"19 (A$)
GPA: 3.4
WE:Engineering (Manufacturing)
Send PM
Reviews Badge
Re: If b is positive, is ab positive? [#permalink] New post   11 Aug 2017, 04:27
1
Kudos
I would go for E as well.
1) A^2b > 0 A can be any value and so can B (positive)

2) A^2+B =13
A^2 can be 12
B can be 1
or A^2 (-1^2) can 1
B can be 12

both 1 and 2 - No difference.

I hope its correct
User avatar
L
pushpitkc
Senior PS Moderator
Joined: 26 Feb 2016
Posts: 2873
Own Kudos [?]: 5206 [0]
Given Kudos: 47
Location: India
GPA: 3.12
Send PM
Re: If b is positive, is ab positive? [#permalink] New post   11 Aug 2017, 05:42
If b is positive, is ab positive?

1. \(a^2b>0\)

Since we are given b is positive,
if a is either positive or negative, the expression \(a^2b>0\) holds true.
Case 1: a=-3, b=2 Here, ab is negative
Case 2: a=3, b=2 Here, ab is positive(Insufficient)

2. \(a^2+b=13\)

Since we are given b is positive,
if a is either positive or negative, the expression \(a^2+b=13\) holds true.
Case 1: a=-3, b=5 Here, ab is negative
Case 2: a=3, b=5 Here, ab is positive(Insufficient)

Even combining both the statements, we will be left with two options
in the first one - both a and b are positive
in the second one - a is negative and b is positive. (Insufficient)(Option E)
User avatar
P
sahilvijay
Senior Manager
Senior Manager
Joined: 29 Jun 2017
Posts: 312
Own Kudos [?]: 798 [0]
Given Kudos: 76
GPA: 4
WE:Engineering (Transportation)
Send PM
GMAT ToolKit User Reviews Badge
Re: If b is positive, is ab positive? [#permalink] New post   11 Aug 2017, 08:32
given b>0
1) (a^2).b>0 from this b>0 then a can be positive as well as negative, so sign of axb can't be determined. A,D ruled out
2) (a^2)+b=13 , b>0 and b <13 a can have Positive and Negative values, also if b>13 , then a is not defined hence sign of axb can't be determined. B ruled out.

Combining both ,
a^2+b = 13 and (a^2) x b > 0 cant solve the problem with the sign from above 2 statements, a can be negative as well as positive since its square will always be positive and therefore C ruled out

Answer is E
User avatar
B
SaGa
Intern
Intern
Joined: 15 Mar 2017
Posts: 27
Own Kudos [?]: 221 [0]
Given Kudos: 39
Location: India
Concentration: International Business, Strategy
Schools: Kellogg '20 ISB '20 Tuck '20
GMAT 1: 720 Q50 V37
GPA: 4
Send PM
Re: If b is positive, is ab positive? [#permalink] New post   11 Aug 2017, 10:18
+1 E

a^2*b>0
a can be both positive and negative

a^2 + b = 13
a can be both positive and negative

Even combining both we do not get if a is positive or negative
Hence E
User avatar
B
prerakgoel03
Intern
Intern
Joined: 05 Feb 2017
Posts: 27
Own Kudos [?]: 25 [0]
Given Kudos: 50
Send PM
Re: If b is positive, is ab positive? [#permalink] New post   11 Aug 2017, 11:52
St:1 says nothing but what is given in question. B is positive. A can be -ve as well as +ve.Insufficient
St:2 says that a2 will be positive .Again A can be -ve as well as +ve.Insufficient

Combining does not help either. Therefore E.
avatar
S
AD2GMAT
Manager
Manager
Joined: 30 Jul 2014
Status:MBA Completed
Affiliations: IIM
Posts: 91
Own Kudos [?]: 97 [0]
Given Kudos: 107
Send PM
Reviews Badge
Re: If b is positive, is ab positive? [#permalink] New post   07 Sep 2017, 04:10
Silly Mistake, I did -> assumed that a is positive in place b - marked option D that is incorrect :(
User avatar
bumpbot
Non-Human User
Joined: 09 Sep 2013
Posts: 32680
Own Kudos [?]: 822 [0]
Given Kudos: 0
Send PM
Re: If b is positive, is ab positive? 1)a^2b >0 2)a^2 + b=13 [#permalink] New post   19 Oct 2019, 06:54
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
GMAT Club Bot
gmatclubot
Re: If b is positive, is ab positive? 1)a^2b >0 2)a^2 + b=13 [#permalink]
19 Oct 2019, 06:54
Moderator:
Bunuel
Math Expert
92915 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne
Main navigation
GMAT Resources
Partners
MBA Resources
www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions