Author 
Message 
TAGS:

Hide Tags

Manager
Joined: 09 Dec 2009
Posts: 119

If x^2y^3 = 200, what is xy ?
[#permalink]
Show Tags
09 Apr 2010, 20:14
Question Stats:
55% (01:27) correct 45% (01:39) wrong based on 485 sessions
HideShow timer Statistics
If \(x^2y^3 = 200\), what is xy ? (1) y is an integer (2) x/y = 2.5 I get why 1 is NSF, no info on x. But with stmt 2, isnt it also NSF b/c we cant confirm if x is neg or positive or not?
Official Answer and Stats are available only to registered users. Register/ Login.
_________________
G.T.L.  GMAT, Tanning, Laundry
Round 1: 05/12/10 http://gmatclub.com/forum/handlingagrenadethesituationsofficialdebrief94181.html
Round 2: 07/10/10  This time it's personal.




Math Expert
Joined: 02 Sep 2009
Posts: 49271

Re: If x^2y^3 = 200, what is xy ?
[#permalink]
Show Tags
14 Apr 2010, 02:53
TheSituation wrote: If x^2y^3=200 , what is xy ? 1. y is an integer 2. x/y=2.5 I get why 1 is NSF, no info on x. But with stmt 2, isnt it also NSF b/c we cant confirm if x is neg or positive or not? If \(x^2y^3=200\), what is \(xy\)? (1) \(y\) is an integer > \(y\) can be any positive integer and there will be two values of \(x\) for each \(y\) to satisfy \(x^2y^3=200\). For example \(y=10\) > \(x^2y^3=x^2*1000=200\) > \(x=\frac{1}{\sqrt{5}}\) or \(x=\frac{1}{\sqrt{5}}\). So there are infinite values of \(xy\). Not sufficient. (2) \(\frac{x}{y}=2.5\) > \(x=2.5y\). We have two equations and two variables > \(x^2y^3=6.25y^5=200\) > \(y^5=32\) > \(y=2\), \(x=5\) > \(xy=10\). Sufficient. Answer: B.
_________________
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




CEO
Status: Nothing comes easy: neither do I want.
Joined: 12 Oct 2009
Posts: 2617
Location: Malaysia
Concentration: Technology, Entrepreneurship
GMAT 1: 670 Q49 V31 GMAT 2: 710 Q50 V35

Re: If x^2y^3 = 200, what is xy ?
[#permalink]
Show Tags
09 Apr 2010, 23:14
x^2 * y^3 = 200 since x^2 is +ve, then y must be positive to satisfy this. now if x/y = 2.5 , if y is +_ve then x is also +ve. I hope this helps
_________________
Fight for your dreams :For all those who fear from Verbal lets give it a fight
Money Saved is the Money Earned
Jo Bole So Nihaal , Sat Shri Akaal
Support GMAT Club by putting a GMAT Club badge on your blog/Facebook
GMAT Club Premium Membership  big benefits and savings
Gmat test review : http://gmatclub.com/forum/670to710alongjourneywithoutdestinationstillhappy141642.html



Manager
Joined: 09 Dec 2009
Posts: 119

Re: If x^2y^3 = 200, what is xy ?
[#permalink]
Show Tags
10 Apr 2010, 10:09
Thanks gurpreet. This is another good example of a question that isnt that hard, but when ive been studying for too long I'll get confused. Thanks again.
_________________
G.T.L.  GMAT, Tanning, Laundry
Round 1: 05/12/10 http://gmatclub.com/forum/handlingagrenadethesituationsofficialdebrief94181.html
Round 2: 07/10/10  This time it's personal.



CEO
Status: Nothing comes easy: neither do I want.
Joined: 12 Oct 2009
Posts: 2617
Location: Malaysia
Concentration: Technology, Entrepreneurship
GMAT 1: 670 Q49 V31 GMAT 2: 710 Q50 V35

Re: If x^2y^3 = 200, what is xy ?
[#permalink]
Show Tags
10 Apr 2010, 10:48
solve question only when your mind is fresh....if u feel sluggish, take a small nap. Good luck.
_________________
Fight for your dreams :For all those who fear from Verbal lets give it a fight
Money Saved is the Money Earned
Jo Bole So Nihaal , Sat Shri Akaal
Support GMAT Club by putting a GMAT Club badge on your blog/Facebook
GMAT Club Premium Membership  big benefits and savings
Gmat test review : http://gmatclub.com/forum/670to710alongjourneywithoutdestinationstillhappy141642.html



Manager
Joined: 05 Mar 2010
Posts: 180

Re: If x^2y^3 = 200, what is xy ?
[#permalink]
Show Tags
13 Apr 2010, 12:34
Stmt 1. y is an integer to satisfy x^2 y^3 = 200 ............ y should be positive integer but x can be negative or positive Insufficient stmt. 2 x/y =2.5 ....... now to satify the given condition y should be positive then x has to be positive Sufficient IMO B
_________________
Success is my Destiny



Manager
Joined: 28 Sep 2011
Posts: 62
Location: United States
GMAT 1: 520 Q34 V27 GMAT 3: 690 Q47 V38
GPA: 3.01
WE: Information Technology (Commercial Banking)

Re: If x^2y^3 = 200, what is xy ?
[#permalink]
Show Tags
08 May 2012, 08:24
I got this problem wrong. Bunuel, can you explain if I approached it the wrong way.
I factored out 200, which = \(2^3 * 5^2\).
After this its obvious \(xy = 10\)
What am i missing here?



Math Expert
Joined: 02 Sep 2009
Posts: 49271

Re: If x^2y^3 = 200, what is xy ?
[#permalink]
Show Tags
09 May 2012, 02:06
ashish8 wrote: I got this problem wrong. Bunuel, can you explain if I approached it the wrong way.
I factored out 200, which = \(2^3 * 5^2\).
After this its obvious \(xy = 10\)
What am i missing here? Check my post above: ifx2y3200whatisxy1yisaninteger2xy25b92486.html#p713396First of all \(x^2y^3=2^3*5^2\) has infinitely many solutions for \(x\) and \(y\). For ANY (nonzero) value of \(x\) there exist some \(y\) to satisfy \(x^2y^3=200\) and viseversa. For example \(x=1\) and \(y=\sqrt[3]{200}\), or \(x=10\) and \(y=\sqrt[3]{2}\), ... As you can see it's not necessary for \(x\) and \(y\) to be integers (3 and 2) to satisfy the given equation. As for (1): \(y\) is an integer. \(y\) can be any positive integer and there will be two values of \(x\) for each \(y\) to satisfy \(x^2y^3=200\). For example \(y=10\) > \(x^2y^3=x^2*1000=200\) > \(x=\frac{1}{\sqrt{5}}\) or \(x=\frac{1}{\sqrt{5}}\). So there are infinite values of \(xy\). Not sufficient. Hope it's clear.
_________________
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: 06 Apr 2010
Posts: 72

Re: If x^2y^3 = 200, what is xy ?
[#permalink]
Show Tags
23 May 2012, 04:52
ashish8 wrote: I got this problem wrong. Bunuel, can you explain if I approached it the wrong way.
I factored out 200, which = \(2^3 * 5^2\).
After this its obvious \(xy = 10\)
What am i missing here? Be careful when 1.the number type is not statedthat could be any type,integer,real etc 2.you see factorization type questionthey are not always integer or prime number,unless explicitly stated. common mistakes for me..even after months of studying



Intern
Joined: 12 Dec 2013
Posts: 16

Re: If x^2y^3 = 200, what is xy ?
[#permalink]
Show Tags
19 Oct 2014, 01:34
Hi Bunuel,
With regards to the problem above, for st 2, is it fine to approach it the following way 
(2) x/y = 2.5 x/y = 25/10 => 5/2 therefore, x = 5 & y = 2. giving xy = 10 Suff.
please do let me know! Thanks in advance!



Math Expert
Joined: 02 Sep 2009
Posts: 49271

Re: If x^2y^3 = 200, what is xy ?
[#permalink]
Show Tags
20 Oct 2014, 03:27



Intern
Joined: 12 Dec 2013
Posts: 16

Re: If x^2y^3 = 200, what is xy ?
[#permalink]
Show Tags
20 Oct 2014, 09:28
Thank you so much for clearing that doubt!



Intern
Joined: 20 Dec 2014
Posts: 38

Re: If x^2y^3 = 200, what is xy ?
[#permalink]
Show Tags
27 Mar 2018, 06:56
TheSituation wrote: If x^2y^3 = 200, what is xy ? (1) y is an integer (2) x/y = 2.5 I get why 1 is NSF, no info on x. But with stmt 2, isnt it also NSF b/c we cant confirm if x is neg or positive or not? The question needs to be worded better. X^2 * Y^3 I interpreted the question as (X^2y)^3
_________________
Kindly press "+1 Kudos" to appreciate



Math Expert
Joined: 02 Sep 2009
Posts: 49271

Re: If x^2y^3 = 200, what is xy ?
[#permalink]
Show Tags
27 Mar 2018, 07:29



Intern
Joined: 20 Dec 2014
Posts: 38

If x^2y^3 = 200, what is xy ?
[#permalink]
Show Tags
27 Mar 2018, 10:59
Bunuel wrote: MT1988 wrote: TheSituation wrote: If x^2y^3 = 200, what is xy ? (1) y is an integer (2) x/y = 2.5 I get why 1 is NSF, no info on x. But with stmt 2, isnt it also NSF b/c we cant confirm if x is neg or positive or not? The question needs to be worded better. X^2 * Y^3 I interpreted the question as (X^2y)^3 Edited, thank you. Though mathematically x^2y^3 can only mean \(x^2y^3\). If it were \((x^2y)^3\) it would be written as (x^2y)^3 and if it were \((x^{2y})^3\) it would be written as (x^(2y))^3 PEMDAS.... Was wondering what if my interpretation was correct? Are there questions like that? Took for ever to solve but if my interpretation was right would B be the answer? Am I unnecessarily complicating the question?
_________________
Kindly press "+1 Kudos" to appreciate



Manager
Joined: 30 Mar 2017
Posts: 136

Re: If x^2y^3 = 200, what is xy ?
[#permalink]
Show Tags
23 Jun 2018, 09:07
Bunuel wrote: TheSituation wrote: If x^2y^3=200 , what is xy ? 1. y is an integer 2. x/y=2.5 I get why 1 is NSF, no info on x. But with stmt 2, isnt it also NSF b/c we cant confirm if x is neg or positive or not? If \(x^2y^3=200\), what is \(xy\)? (1) \(y\) is an integer > \(y\) can be any positive integer and there will be two values of \(x\) for each \(y\) to satisfy \(x^2y^3=200\). For example \(y=10\) > \(x^2y^3=x^2*1000=200\) > \(x=\frac{1}{\sqrt{5}}\) or \(x=\frac{1}{\sqrt{5}}\). So there are infinite values of \(xy\). Not sufficient. (2) \(\frac{x}{y}=2.5\) > \(x=2.5y\). We have two equations and two variables > \(x^2y^3=6.25y^5=200\) > \(y^5=32\) > \(y=2\), \(x=5\) > \(xy=10\). Sufficient. Answer: B. For Statement 2, I think we can stop at this step: \(6.25y^5=200\) y is raised to an odd power, so there will be one solution. we can find y... we can find x.




Re: If x^2y^3 = 200, what is xy ? &nbs
[#permalink]
23 Jun 2018, 09:07






