Apr 27 07:00 AM PDT  09:00 AM PDT Attend this webinar and master GMAT SC in 10 days by learning how meaning and logic can help you tackle 700+ level SC questions with ease. Apr 28 07:00 AM PDT  09:00 AM PDT Attend this webinar to learn a structured approach to solve 700+ Number Properties question in less than 2 minutes. Apr 29 08:00 AM PDT  09:00 AM PDT Join a free live webinar and learn timemanagement tactics that will guarantee you answer all questions, in all sections, on time. Save your spot today! Apr 30 10:00 PM PDT  11:00 PM PDT Enter to win 3 full months of access to EMPOWERgmat's groundbreaking GMAT prep course. Prize includes all 6 GMAT Official Practice exams and access to the GMAT Club Test & Quiz Bank Pack. May 01 10:00 PM PDT  11:00 PM PDT Target Test Prep is kicking off spring with a fresh giveaway contest! For a limited time, you have a chance to win 4 months of full, FREE access to our 5star rated GMAT Quant course.
Author 
Message 
TAGS:

Hide Tags

Intern
Joined: 16 Aug 2012
Posts: 1

If a > 0, is 2/(a+b) + 2/(ab) = 1?
[#permalink]
Show Tags
Updated on: 29 Apr 2013, 00:14
Question Stats:
67% (01:46) correct 33% (02:06) wrong based on 255 sessions
HideShow timer Statistics
If a > 0, is 2/(a+b) + 2/(ab) = 1? (1) b = 0 (2) a^2 − b^2 = 4a My answer was D. I thought that STATEMENT 1 was SUFFICIENT to answer the question, because the question is not asking if the equation is 1 or not. It is asking if the info provided is SUFFICIENT to answer the question or not.
Thanks
Official Answer and Stats are available only to registered users. Register/ Login.
Originally posted by ahatoval on 28 Apr 2013, 20:10.
Last edited by Bunuel on 29 Apr 2013, 00:14, edited 1 time in total.
Renamed the topic and edited the question.



Verbal Forum Moderator
Joined: 10 Oct 2012
Posts: 611

Re: Special a & b
[#permalink]
Show Tags
28 Apr 2013, 22:04
ahatoval wrote: Hey guys,
I need your help again. Could anybody please explain why the answer is B?
If a > 0, is 2/(a+b) + 2/(ab) = 1?
(1) b = 0 (2) a^2 − b^2 = 4a
My answer was D. I thought that STATEMENT 1 was SUFFICIENT to answer the question, because the question is not asking if the equation is 1 or not. It is asking if the info provided is SUFFICIENT to answer the question or not.
Thanks From F.S 1, we know that the given expression condenses to 2/a+2/a = 4/a. The question stem asks, whether this is equal to 1. For a=4, we will have an affirmative answer, however for a=2,we would not get 1. Thus, as the answer from F.S 1, depends on the value of a, which is not unique, Statement A is not sufficient. From F.S 2, we can simplify the given statement as\(\frac{[2(ab)+2(a+b)]}{a^2b^2} = \frac{4a}{a^2b^2}\)= 4a/4a = 1[a is not equal to zero]. Thus F.S 2 is infact sufficient. B.
_________________



Manager
Status: Pushing Hard
Affiliations: GNGO2, SSCRB
Joined: 30 Sep 2012
Posts: 78
Location: India
Concentration: Finance, Entrepreneurship
GPA: 3.33
WE: Analyst (Health Care)

Re: Special a & b
[#permalink]
Show Tags
28 Apr 2013, 23:45
ahatoval wrote: Hey guys,
I need your help again. Could anybody please explain why the answer is B?
If a > 0, is 2/(a+b) + 2/(ab) = 1?
(1) b = 0 (2) a^2 − b^2 = 4a
My answer was D. I thought that STATEMENT 1 was SUFFICIENT to answer the question, because the question is not asking if the equation is 1 or not. It is asking if the info provided is SUFFICIENT to answer the question or not.
Thanks  Okay...... First it is given that a>0, Now, Question asks Is 2/(a+b) +2/(ab) = 1 ?? That means Is Left Hand Side = Right Hand Side?? Now, First Rephrase the Question. I.e., 2/(a+b) +2/(ab) = 1 ⇒ (2a2b+2a+2b)/(a^2b^2 ) = 1 ⇒ (2a+2a)/(a^2b^2 ) = 1 ⇒ 4a/(a^2b^2 ) =1 ?? , So the Question basically asks :: Is 4a/(a^2b^2 ) =1 ? Statement: 1 Says b=0 if we plugin b=0 in the equation given, the LHS ≠ RHS. Therefore, It is clearly insufficient. Statement: 2 says a2 – b2 = 4a, Now, when you plugin a2 – b2 = 4a in the equation provided in the Question, You will get Left Hand Side = Right Hand Side. Therefore, it is sufficient. Hence, B only.
_________________
If you don’t make mistakes, you’re not working hard. And Now that’s a Huge mistake.



Intern
Joined: 30 Apr 2013
Posts: 34

Re: If a > 0, is 2/(a+b) + 2/(ab) = 1?
[#permalink]
Show Tags
30 Apr 2013, 21:10
I am still confused. Your explanation says Statement 1 LHS is not equal to RHS ...doesn't that mean it is sufficient in saying whether the first statement is enough or not? I too selected D and cannot understand why A is not sufficient to answer the question...perhaps require an explanation from a different angle ??



Senior Manager
Joined: 16 Dec 2011
Posts: 299

Re: If a > 0, is 2/(a+b) + 2/(ab) = 1?
[#permalink]
Show Tags
30 Apr 2013, 21:22
rsworase wrote: I am still confused. Your explanation says Statement 1 LHS is not equal to RHS ...doesn't that mean it is sufficient in saying whether the first statement is enough or not? I too selected D and cannot understand why A is not sufficient to answer the question...perhaps require an explanation from a different angle ?? Statement 1 says b=0, but there is no information on a. If a = 4, only then we will have 2/(a+b) + 2/(ab) = 1. Without any information on a, neither we can say LHS = RHS, nor we can say LHS # RHS. Hence, statement 1 is insufficient.



Manager
Joined: 21 Jun 2011
Posts: 60
Location: United States
Concentration: Accounting, Finance
WE: Accounting (Accounting)

Re: If a > 0, is 2/(a+b) + 2/(ab) = 1?
[#permalink]
Show Tags
02 Mar 2015, 03:08
ahatoval wrote: If a > 0, is 2/(a+b) + 2/(ab) = 1? (1) b = 0 (2) a^2 − b^2 = 4a My answer was D. I thought that STATEMENT 1 was SUFFICIENT to answer the question, because the question is not asking if the equation is 1 or not. It is asking if the info provided is SUFFICIENT to answer the question or not.
Thanks I got the answer as D. From Statement 1, I got the value for a=4, substituting the value of a and b in the above equation proves that the expression is equal to 1. Not sure what am I missing here.



EMPOWERgmat Instructor
Status: GMAT Assassin/CoFounder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 13976
Location: United States (CA)

Re: If a > 0, is 2/(a+b) + 2/(ab) = 1?
[#permalink]
Show Tags
02 Mar 2015, 14:33
Hi davidfrank, In this question, we're told that A > 0. We're ASKED if 2/(A+B) + 2/(AB) = 1. This is a YES/NO question. Fact 1: B = 0 We don't know what A is, so let's TEST VALUES.... IF.... A = 1 2/(1) + 2/(1) = 4 and the answer to the question is NO. IF.... A = 4 2/(4) + 2/(4) = 1 and the answer to the question is YES. Fact 1 is INSUFFICIENT GMAT assassins aren't born, they're made, Rich
_________________
760+: Learn What GMAT Assassins Do to Score at the Highest Levels Contact Rich at: Rich.C@empowergmat.com*****Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!*****
Rich Cohen
CoFounder & GMAT Assassin
Special Offer: Save $75 + GMAT Club Tests Free
Official GMAT Exam Packs + 70 Pt. Improvement Guarantee www.empowergmat.com/



Intern
Joined: 16 Jul 2017
Posts: 3

Re: If a > 0, is 2/(a+b) + 2/(ab) = 1?
[#permalink]
Show Tags
16 Jul 2017, 23:56
I know the answer is B, but I chose A.
The question simplified: 4a = (a+b) (ab)
1.) If b = 0, then a has to equal to 4, then we can plug in a and b to to figure if [2/(a+b)] +[2/(ab)] = 1 ? b+ 0 4a = (a+b) (ab) = (a^2)(b^2) 4a = (a+0) (a0) = (a^2)(0) a = 4
2.) I understand when you simplify the question, you get the same statement as statement two. However, I am having a hard time interpreting how this helps determine if statement is equal to 1. How can I figure if 4a = (a+b) (ab) = (a^2)(b^2) is equal to 1 ?
Am I missing something or assuming something extra?



Math Expert
Joined: 02 Sep 2009
Posts: 54544

Re: If a > 0, is 2/(a+b) + 2/(ab) = 1?
[#permalink]
Show Tags
17 Jul 2017, 00:21
thealchemist89 wrote: I know the answer is B, but I chose A.
The question simplified: 4a = (a+b) (ab)
1.) If b = 0, then a has to equal to 4, then we can plug in a and b to to figure if [2/(a+b)] +[2/(ab)] = 1 ? b+ 0 4a = (a+b) (ab) = (a^2)(b^2) 4a = (a+0) (a0) = (a^2)(0) a = 4
2.) I understand when you simplify the question, you get the same statement as statement two. However, I am having a hard time interpreting how this helps determine if statement is equal to 1. How can I figure if 4a = (a+b) (ab) = (a^2)(b^2) is equal to 1 ?
Am I missing something or assuming something extra? If a > 0, is 2/(a+b) + 2/(ab) = 1?Is \(\frac{2}{(a+b)} + \frac{2}{(ab)} = 1\)? Is \(a^2 − b^2 = 4a\)? (This is the question we want to answer). (1) b = 0. The question becomes: is \(a^2 = 4a\)? Since given that a > 0, this is equivalent to: is \(a = 4\)? We don't know that. a can be any positive number. Not sufficient. (2) \(a^2 − b^2 = 4a\). Directly gives an YES answer to the question. Sufficient. Answer: B.
_________________



Intern
Joined: 08 Mar 2015
Posts: 2

Re: If a > 0, is 2/(a+b) + 2/(ab) = 1?
[#permalink]
Show Tags
23 Aug 2017, 10:34
The answer should be C. It is essential to mention that a not equal to b, which is not done in the given details. But if we consider the given fact a>0 and statement 1: b=0 together, this can be true only if b=0, a>0 which means a not equal to be.



Intern
Joined: 18 Aug 2017
Posts: 30

Re: If a > 0, is 2/(a+b) + 2/(ab) = 1?
[#permalink]
Show Tags
25 Aug 2017, 00:44
viswanathnittala wrote: The answer should be C. It is essential to mention that a not equal to b, which is not done in the given details. But if we consider the given fact a>0 and statement 1: b=0 together, this can be true only if b=0, a>0 which means a not equal to be. Because statement 1 is INSUFF, statement 2 is SUFF, therefore the answer can't be C.



Intern
Joined: 30 May 2017
Posts: 14

Re: If a > 0, is 2/(a+b) + 2/(ab) = 1?
[#permalink]
Show Tags
25 Aug 2017, 00:53
I am unable to see options for any DS question. Can anyone help as soon as possible?



Math Expert
Joined: 02 Sep 2009
Posts: 54544

Re: If a > 0, is 2/(a+b) + 2/(ab) = 1?
[#permalink]
Show Tags
25 Aug 2017, 00:58
aksh5900 wrote: I am unable to see options for any DS question. Can anyone help as soon as possible? This is a data sufficiency question. Options for DS questions are always the same. The data sufficiency problem consists of a question and two statements, labeled (1) and (2), in which certain data are given. You have to decide whether the data given in the statements are sufficient for answering the question. Using the data given in the statements, plus your knowledge of mathematics and everyday facts (such as the number of days in July or the meaning of the word counterclockwise), you must indicate whether— A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient to answer the question asked. B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient to answer the question asked. C. BOTH statements (1) and (2) TOGETHER are sufficient to answer the question asked, but NEITHER statement ALONE is sufficient to answer the question asked. D. EACH statement ALONE is sufficient to answer the question asked. E. Statements (1) and (2) TOGETHER are NOT sufficient to answer the question asked, and additional data specific to the problem are needed. I suggest you to go through the following posts: ALL YOU NEED FOR QUANT. Ultimate GMAT Quantitative MegathreadHope this helps.
_________________



Director
Joined: 12 Nov 2016
Posts: 725
Location: United States
GPA: 2.66

Re: If a > 0, is 2/(a+b) + 2/(ab) = 1?
[#permalink]
Show Tags
10 Sep 2017, 13:09
ahatoval wrote: If a > 0, is 2/(a+b) + 2/(ab) = 1? (1) b = 0 (2) a^2 − b^2 = 4a My answer was D. I thought that STATEMENT 1 was SUFFICIENT to answer the question, because the question is not asking if the equation is 1 or not. It is asking if the info provided is SUFFICIENT to answer the question or not.
Thanks With algebra ds always try to see if you can rewrite the original equation to find the hidden inference/question 2(ab) + 2(a +b) / a^2b^2 2a2b +2a +2b/a^2b^2 4a/ a^2b^2 St 1 We don't know what A is and even if we cancel out terms we could still have different scenarios (e.x if A is 1 vs 3 the answer will be different) insuff St 2 Essentially 4a/4a = 1 suff B




Re: If a > 0, is 2/(a+b) + 2/(ab) = 1?
[#permalink]
10 Sep 2017, 13:09






