GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 21 Oct 2019, 04:20

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.

Close

Request Expert Reply

Confirm Cancel

If x and y are positive numbers and z = xy^2, a 50 percent increase

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Find Similar Topics 
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 58421
If x and y are positive numbers and z = xy^2, a 50 percent increase  [#permalink]

Show Tags

New post 09 Nov 2015, 00:00
1
2
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

79% (01:42) correct 21% (02:03) wrong based on 141 sessions

HideShow timer Statistics

Math Expert
avatar
V
Joined: 02 Aug 2009
Posts: 8003
Re: If x and y are positive numbers and z = xy^2, a 50 percent increase  [#permalink]

Show Tags

New post 09 Nov 2015, 03:59
1
1
Bunuel wrote:
If x and y are positive numbers and z = xy^2, a 50 percent increase in x and a 20 percent decrease in y would result in which of the following changes in z?

(A) A decrease of 4%
(B) A decrease of 14%
(C) An increase of 4%
(D) An increase of 20%
(E) An increase of 30%


z=x*y^2
Z=1.5 x*(0.8)^2=.96x*y^2=.96z
so a decrease of 4%
A
_________________
Verbal Forum Moderator
User avatar
V
Status: Greatness begins beyond your comfort zone
Joined: 08 Dec 2013
Posts: 2402
Location: India
Concentration: General Management, Strategy
Schools: Kelley '20, ISB '19
GPA: 3.2
WE: Information Technology (Consulting)
GMAT ToolKit User Reviews Badge CAT Tests
Re: If x and y are positive numbers and z = xy^2, a 50 percent increase  [#permalink]

Show Tags

New post 10 Nov 2015, 07:57
1
z= x*y^2

Now , since x increases by 50 % and y decreases by 20 %
z'=(3/2)x * (8/10)(8/10)y^2
= 192/200 * x*y^2
= 96/100 * x*y^2
= 96/100 * z

a decrease in 4 %

Answer A
_________________
When everything seems to be going against you, remember that the airplane takes off against the wind, not with it. - Henry Ford
The Moment You Think About Giving Up, Think Of The Reason Why You Held On So Long
VP
VP
User avatar
D
Joined: 05 Mar 2015
Posts: 1000
Reviews Badge
Re: If x and y are positive numbers and z = xy^2, a 50 percent increase  [#permalink]

Show Tags

New post 17 Apr 2016, 05:19
1
Bunuel wrote:
If x and y are positive numbers and z = xy^2, a 50 percent increase in x and a 20 percent decrease in y would result in which of the following changes in z?

(A) A decrease of 4%
(B) A decrease of 14%
(C) An increase of 4%
(D) An increase of 20%
(E) An increase of 30%


Just take smart numbers
x=4 and y=5-----> z=100
a 50 percent increase in x ---->x=6
a 20 percent decrease in y----->y=4
now z=6*4^2---->96
so Z decreased from 100 to 96
Ans A
Senior Manager
Senior Manager
User avatar
G
Joined: 24 Nov 2015
Posts: 490
Location: United States (LA)
Reviews Badge
Re: If x and y are positive numbers and z = xy^2, a 50 percent increase  [#permalink]

Show Tags

New post 30 Apr 2016, 14:09
Given fact z = \(xy^2\)
A 50% increase in x = 1.5x
A 20% decrease in y = 0.8y
calculating z = \(xy^2\)
change in z = \(1.5x\) * \(0.8y^2\)
so z = 0.96 times original z
clearly its a 4 % decrease
correct answer - A
Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 13345
Re: If x and y are positive numbers and z = xy^2, a 50 percent increase  [#permalink]

Show Tags

New post 07 Oct 2018, 08:30
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
Re: If x and y are positive numbers and z = xy^2, a 50 percent increase   [#permalink] 07 Oct 2018, 08:30
Display posts from previous: Sort by

If x and y are positive numbers and z = xy^2, a 50 percent increase

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  





Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne