Author 
Message 
TAGS:

Hide Tags

Manager
Joined: 26 Oct 2010
Posts: 59

If wx = y, then what is the value of xy?
[#permalink]
Show Tags
31 Dec 2010, 04:51
Question Stats:
65% (00:43) correct 35% (01:08) wrong based on 321 sessions
HideShow timer Statistics
If wx = y, then what is the value of xy? (1) w*x^2 = 16 (2) y = 4
Official Answer and Stats are available only to registered users. Register/ Login.




Math Expert
Joined: 02 Sep 2009
Posts: 48097

Re: If wx = y, then what is the value of xy?
[#permalink]
Show Tags
31 Dec 2010, 06:22




Manager
Joined: 26 Oct 2010
Posts: 59

Re: If wx = y, then what is the value of xy?
[#permalink]
Show Tags
31 Dec 2010, 07:08
super thanks! should have seen it was that easy



Manager
Status: what we want to do, do it as soon as possible
Joined: 24 May 2010
Posts: 90
Location: Vietnam
WE 1: 5.0

Re: If wx = y, then what is the value of xy?
[#permalink]
Show Tags
01 Jan 2011, 08:45
+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.
_________________
Consider giving me kudos if you find my explanations helpful so i can learn how to express ideas to people more understandable.



Intern
Joined: 05 Mar 2014
Posts: 5

Re: If wx = y, then what is the value of xy?
[#permalink]
Show Tags
05 Mar 2014, 09:45
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.



Board of Directors
Joined: 17 Jul 2014
Posts: 2717
Location: United States (IL)
Concentration: Finance, Economics
GPA: 3.92
WE: General Management (Transportation)

Re: If wx = y, then what is the value of xy?
[#permalink]
Show Tags
28 Oct 2015, 21:27
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: 48097

Re: If wx = y, then what is the value of xy?
[#permalink]
Show Tags
29 Oct 2015, 00:22



Board of Directors
Joined: 17 Jul 2014
Posts: 2717
Location: United States (IL)
Concentration: Finance, Economics
GPA: 3.92
WE: General Management (Transportation)

Re: If wx = y, then what is the value of xy?
[#permalink]
Show Tags
29 Oct 2015, 06:55
Bunuel wrote: 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. Thanks bunuel, but it was not needed. I admit that it was my mistake, and that I should have been more attentive. Indeed wx^2 represents w*x^2 I was speaking about \(wx^2\) rewriting in this format



Manager
Joined: 19 Jun 2017
Posts: 50
GMAT 1: 660 Q39 V40 GMAT 2: 700 Q45 V41

Re: If wx = y, then what is the value of xy?
[#permalink]
Show Tags
10 Dec 2017, 03:22
I'm sorry, I've spent 20 mins trying to puzzle this out but just can't get it.
What if we were to pick numbers?
WX=Y
If W were 1 and X were 4, then Y would be 4.
Using statement 1; WX^2 = 16 would mean 1 x 4^2 = 16
This satisfied the number I'd picked earlier and Y remains 4.
But if I had chosen W as 16 and X as 1, then WX = 16
Using statement one > 16 x 1^2 = 16
This also satisfied picking W as 16 and X as 1, but now the value of WX is 16 wich means that Y is also 16.
So i get two different possible values for Y: 4 and 16.
What am I doing wrong?



Math Expert
Joined: 02 Sep 2009
Posts: 48097

Re: If wx = y, then what is the value of xy?
[#permalink]
Show Tags
10 Dec 2017, 04:09
calappa1234 wrote: I'm sorry, I've spent 20 mins trying to puzzle this out but just can't get it.
What if we were to pick numbers?
WX=Y
If W were 1 and X were 4, then Y would be 4.
Using statement 1; WX^2 = 16 would mean 1 x 4^2 = 16
This satisfied the number I'd picked earlier and Y remains 4.
But if I had chosen W as 16 and X as 1, then WX = 16
Using statement one > 16 x 1^2 = 16
This also satisfied picking W as 16 and X as 1, but now the value of WX is 16 wich means that Y is also 16.
So i get two different possible values for Y: 4 and 16.
What am I doing wrong? What question are you answering? The question asks: what is the value of xy? In both of your examples xy comes to be 16.
_________________
New to the Math Forum? Please read this: Ultimate GMAT Quantitative Megathread  All You Need for Quant  PLEASE READ AND FOLLOW: 12 Rules for Posting!!! Resources: GMAT Math Book  Triangles  Polygons  Coordinate Geometry  Factorials  Circles  Number Theory  Remainders; 8. Overlapping Sets  PDF of Math Book; 10. Remainders  GMAT Prep Software Analysis  SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS)  Tricky questions from previous years.
Collection of Questions: PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.
What are GMAT Club Tests? Extrahard Quant Tests with Brilliant Analytics



Manager
Joined: 19 Jun 2017
Posts: 50
GMAT 1: 660 Q39 V40 GMAT 2: 700 Q45 V41

Re: If wx = y, then what is the value of xy?
[#permalink]
Show Tags
10 Dec 2017, 10:25
Oh my, never mind! I've been trying to read way to deep into this question and have in turn, contorted it into something else entirely in my mind. I see now, how simple it actually is. Sorry for the confusion, and thanks for clearing it up!



Intern
Joined: 14 Jul 2017
Posts: 15

Re: If wx = y, then what is the value of xy?
[#permalink]
Show Tags
22 Mar 2018, 21:31
If wx = y, then what is the value of xy?
(1) w*x^2 = 16 (2) y = 4
I solved it like this 1) w*x^2 /x^2 = 16/x^2 (divide by x^2 on both side) w= 16/x^2 Put this in original equation wx = y > (16/x^2)*x = y >16/x = y So, xy = x* (16/x) = 16 Hence, sufficient.
Can we solve it this way aswell??



DS Forum Moderator
Joined: 22 Aug 2013
Posts: 1343
Location: India

Re: If wx = y, then what is the value of xy?
[#permalink]
Show Tags
22 Mar 2018, 22:15
RashmiT wrote: If wx = y, then what is the value of xy?
(1) w*x^2 = 16 (2) y = 4
I solved it like this 1) w*x^2 /x^2 = 16/x^2 (divide by x^2 on both side) w= 16/x^2 Put this in original equation wx = y > (16/x^2)*x = y >16/x = y So, xy = x* (16/x) = 16 Hence, sufficient.
Can we solve it this way aswell?? Hello Yes, I think we can do it this way as well.




Re: If wx = y, then what is the value of xy? &nbs
[#permalink]
22 Mar 2018, 22:15






