NEW HERE? LEARN MORE
closeclose
Last visit was: 26 Apr 2024, 05:12 It is currently 26 Apr 2024, 05:12
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 (ax)16(by)12(cxy)17(dxy)11>0, and all the variables are non-zero,

SORT BY:
Date
Kudos
Tags:
Find Similar Topics 
Show Tags
Hide Tags
User avatar
B
Jamil1992Mehedi
Intern
Intern
Joined: 05 Dec 2017
Posts: 19
Own Kudos [?]: 73 [4]
Given Kudos: 23
GPA: 3.35
Send PM
If (ax)16(by)12(cxy)17(dxy)11>0, and all the variables are non-zero, [#permalink] New post   18 Mar 2018, 01:57
4
Bookmarks
00:00
A
B
C
D
E

Difficulty:

45% (medium)

Question Stats:

63% (01:42) correct 37% (01:42) wrong based on 140 sessions
Hide Show timer Statistics
If \((ax)^{16}(by)^{12}(cxy)^{17}(dxy)^{11}>0\), and all the variables are non-zero numbers, which of the following must be true?

A. ab>0
B. ab<0
C. cd>0
D. cd<0
E. None of the above.
ShowHide Answer
Official Answer
C
User avatar
L
chetan2u
RC & DI Moderator
Joined: 02 Aug 2009
Status:Math and DI Expert
Posts: 11179
Own Kudos [?]: 31944 [1]
Given Kudos: 290
Send PM
Reviews Badge
If (ax)16(by)12(cxy)17(dxy)11>0, and all the variables are non-zero, [#permalink] New post   18 Mar 2018, 05:23
1
Kudos
Expert Reply
Jamil1992Mehedi wrote:
Hi Bunuel, i am confused about the OA. Perhaps my provided ans is wrong. Please Would you share the right ans and difficulty level.
If \((ax)^{16}(by)^{12}(cxy)^{17}(dxy)^{11}>0\), and all the variables are non-zero numbers, which of the following must be true?
A. ab>0
B. ab<0
C. cd>0
D. cd<0
E. None of the above.



Hi,

The OA is flawed. What is the source?

Solution..
\(a^{16}*b^{12}*c^{17}*d^{11}*x^{16+17+11}*y^{12+17+11}>0........a^{16}*b^{12}*c^{17}*d^{11}*x^{44}*y^{40}>0\)..
Now a, b, x and y have even power.
Raised to even power, they would always be POSITIVE. BUT without power, each could be positive or negative. Therefore we cannot comment on their PRODUCT without powers.
So we cannot comment on ab....

Now all other terms with a,b,x and y are positive, so \(c^{17}*d^{11}\) also should be > 0..
Therefore cd>0..
Ans C..
avatar
S
akshata19
Manager
Manager
Joined: 22 May 2017
Posts: 86
Own Kudos [?]: 104 [0]
Given Kudos: 105
Send PM
Re: If (ax)16(by)12(cxy)17(dxy)11>0, and all the variables are non-zero, [#permalink] New post   18 Mar 2018, 10:54
It should be C .
But OA given is A
some please clarify
User avatar
L
Bunuel
Math Expert
Joined: 02 Sep 2009
Posts: 92929
Own Kudos [?]: 619153 [0]
Given Kudos: 81609
Send PM
CAT Tests Forum Quiz Mode
Re: If (ax)16(by)12(cxy)17(dxy)11>0, and all the variables are non-zero, [#permalink] New post   18 Mar 2018, 11:00
Expert Reply
akshata19 wrote:
It should be C .
But OA given is A
some please clarify


OA edited. For clarification is given in the post just above yours.
User avatar
D
Gladiator59
Director
Director
Joined: 16 Sep 2016
Status:It always seems impossible until it's done.
Posts: 645
Own Kudos [?]: 2055 [0]
Given Kudos: 174
GMAT 1: 740 Q50 V40
GMAT 2: 770 Q51 V42
Send PM
GMAT ToolKit User Reviews Badge
Re: If (ax)16(by)12(cxy)17(dxy)11>0, and all the variables are non-zero, [#permalink] New post   18 Mar 2018, 11:11
Jamil1992Mehedi wrote:
If \((ax)^{16}(by)^{12}(cxy)^{17}(dxy)^{11}>0\), and all the variables are non-zero numbers, which of the following must be true?

A. ab>0
B. ab<0
C. cd>0
D. cd<0
E. None of the above.


By pairing of the powers for all other terms.. it turns out c^17 and d^11 are only terms with odd power.
Rest all terms ( including the XY term end up with even powers )
(XY)^17 * (XY)^11 = (XY)^28.

So c and d must have same parity. Either both positive or both negative.

Hence cd > 0.
Option C.
User avatar
B
Jamil1992Mehedi
Intern
Intern
Joined: 05 Dec 2017
Posts: 19
Own Kudos [?]: 73 [0]
Given Kudos: 23
GPA: 3.35
Send PM
Re: If (ax)16(by)12(cxy)17(dxy)11>0, and all the variables are non-zero, [#permalink] New post   20 Mar 2018, 20:00
Thanks Chetan2u and Bunuel for your utmost response.
First of all, in terms of question's source asked by chetan2U, basically i found it in a local GMAT-GRE preparation book. But the question maker claims that product of ab will be positive always due to positive exponent exponent of both a & b. Any cogent argument from your end. Thank you
User avatar
bumpbot
Non-Human User
Joined: 09 Sep 2013
Posts: 32684
Own Kudos [?]: 822 [0]
Given Kudos: 0
Send PM
Re: If (ax)16(by)12(cxy)17(dxy)11>0, and all the variables are non-zero, [#permalink] New post   01 Aug 2019, 23:34
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 (ax)16(by)12(cxy)17(dxy)11>0, and all the variables are non-zero, [#permalink]
01 Aug 2019, 23:34
Moderators:
Bunuel
Math Expert
92929 posts
yashikaaggarwal
Senior Moderator - Masters Forum
3137 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