Last visit was: 23 Jul 2024, 04:36 It is currently 23 Jul 2024, 04:36
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
SORT BY:
Date
Tags:
Show Tags
Hide Tags
User avatar
Manager
Manager
Joined: 26 Oct 2010
Posts: 54
Own Kudos [?]: 94 [84]
Given Kudos: 0
Send PM
Most Helpful Reply
Math Expert
Joined: 02 Sep 2009
Posts: 94580
Own Kudos [?]: 643200 [35]
Given Kudos: 86728
Send PM
General Discussion
User avatar
Manager
Manager
Joined: 26 Oct 2010
Posts: 54
Own Kudos [?]: 94 [2]
Given Kudos: 0
Send PM
User avatar
Manager
Manager
Joined: 24 May 2010
Status:what we want to do, do it as soon as possible
Posts: 50
Own Kudos [?]: 107 [1]
Given Kudos: 315
Location: Vietnam
 Q44  V19 GMAT 2: 570  Q44  V25 GMAT 3: 590  Q48  V23
WE 1: 5.0
Send PM
Re: If wx = y, then what is the value of xy? [#permalink]
+1 for Jonblazon for good question. I got C for uncareful observation
+1 for Bunuel: you are amazing
Thanks once again for your good question, at least to me. :)
avatar
Intern
Intern
Joined: 05 Mar 2014
Posts: 4
Own Kudos [?]: 37 [1]
Given Kudos: 3
Send PM
Re: If wx = y, then what is the value of xy? [#permalink]
1
Kudos
Usually when I have a DS question I try to come up with the equations and respective variables that I need. Then I count the equations and unknowns and if I have more unknowns than I have equations I know it's not sufficient.
Here I'm not sure if the approach is feasible, but I'd like to give it a try. Please give me your opinions on the approach:

1. We have the equation wx = y and we need to find xy = ?. In order to do so we don't need to know x or y, but only w (if we have w, we're able to find xy, as wx = y is given). Therefor w is our only unknown.

(1) we get wx^2=16. As we don't need to handle x as an unknown (see above) we can count what we have: here it's 1 unknown (w) and 1 equation => sufficient
(2) we get y=4. y isn't an unknown in this approach, so when we count: 1 unknown (w) and 0 equations => not sufficient

So it's A.
GMAT Club Legend
GMAT Club Legend
Joined: 19 Dec 2014
Status:GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Posts: 21835
Own Kudos [?]: 11793 [2]
Given Kudos: 450
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Send PM
Re: If wx=y, then what is the value of xy? [#permalink]
1
Kudos
1
Bookmarks
Expert Reply
Hi All,

Most of the DS questions that you'll see on Test Day will be based on patterns of some kind - even if you don't recognize that a pattern is there. As such, sometimes the way to get to the correct answer is to do enough work to PROVE the pattern by TESTing VALUES.

Here, we're told that (W)(X) = Y and we're asked for the value of (X)(Y).

Fact 1: W(X^2) = 16

IF...
W = 16
X = 1
Y = 16
(X)(Y) = 16

W = 16
X = -1
Y = -16
(X)(Y) = 16

W = 4
X = 2
Y = 8
(X)(Y) = 16

W = 4
X = -2
Y = -8
(X)(Y) = 16

W = 1
X = 4
Y = 4
(X)(Y) = 16

W = 1
X = -4
Y = -4
(X)(Y) = 16

The pattern here seems to prove that XY is ALWAYS equal to 16.
Fact 1 is SUFFICIENT

Fact 2: Y = 4

This tells us that...
(W)(X) = 4

IF...
X = 1
(X)(Y) = 4

X = 4
(X)(Y) = 16
Fact 2 is INSUFFICIENT

Final Answer:

GMAT assassins aren't born, they're made,
Rich
Board of Directors
Joined: 17 Jul 2014
Posts: 2145
Own Kudos [?]: 1192 [1]
Given Kudos: 236
Location: United States (IL)
Concentration: Finance, Economics
GMAT 1: 650 Q49 V30
GPA: 3.92
WE:General Management (Transportation)
Send PM
Re: If wx = y, then what is the value of xy? [#permalink]
1
Kudos
i mistakenly took it as (wx)^2
and got wx = +-4 which is insufficient; 2 is as well insufficient..
eh..can't say it's not my fault, but the topic starter should have put the math code here :D
Math Expert
Joined: 02 Sep 2009
Posts: 94580
Own Kudos [?]: 643200 [0]
Given Kudos: 86728
Send PM
Re: If wx = y, then what is the value of xy? [#permalink]
Expert Reply
mvictor wrote:
i mistakenly took it as (wx)^2
and got wx = +-4 which is insufficient; 2 is as well insufficient..
eh..can't say it's not my fault, but the topic starter should have put the math code here :D


The point is that wx^2 mathematically can only mean w*x^2. If it were (wx)^2 it would be written that way. Still edited to avoid confusion.
GMAT Club Legend
GMAT Club Legend
Joined: 12 Sep 2015
Posts: 6804
Own Kudos [?]: 30852 [1]
Given Kudos: 799
Location: Canada
Send PM
Re: If wx = y, then what is the value of xy? [#permalink]
1
Kudos
Expert Reply
Top Contributor
jonblazon wrote:
If wx = y, then what is the value of xy?

(1) w*x^2 = 16
(2) y = 4


Given: wx = y

Target question: What is the value of xy ?

Statement 1: wx²= 16
We can rewrite this as: (wx)(x) = 16
Since wx = y, we can replace wx with y to get: (y)(x) = 16
So, the answer to the target question is xy = 16
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: y = 4
There are several values of w, x and y that satisfy statement 2. Here are two:
Case a: w = 1, x = 4 and y = 4. In this case, the answer to the target question is xy = 16
Case b: w = 2, x = 2 and y = 4. In this case, the answer to the target question is xy = 8
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Answer: A

Cheers,
Brent
GMAT Club Legend
GMAT Club Legend
Joined: 03 Jun 2019
Posts: 5311
Own Kudos [?]: 4244 [1]
Given Kudos: 161
Location: India
GMAT 1: 690 Q50 V34
WE:Engineering (Transportation)
Send PM
Re: If wx = y, then what is the value of xy? [#permalink]
1
Bookmarks
jonblazon wrote:
If wx = y, then what is the value of xy?

(1) w*x^2 = 16
(2) y = 4


Asked: If wx = y, then what is the value of xy?
xy = x*wx = wx^2

(1) w*x^2 = 16
xy = w*x^2 = 16
SUFFICIENT

(2) y = 4
Since x is unknown
NOT SUFFICIENT

IMO A
Manager
Manager
Joined: 05 Jul 2022
Posts: 108
Own Kudos [?]: 16 [0]
Given Kudos: 31
Location: India
WE:Advertising (Health Care)
Send PM
Re: If wx = y, then what is the value of xy? [#permalink]
Do we have to check for positives and negatives in such questions? Is there a rule? I have doubts about such questions...
GMAT Club Bot
Re: If wx = y, then what is the value of xy? [#permalink]
Moderator:
Math Expert
94578 posts