Author 
Message 
TAGS:

Hide Tags

Manager
Joined: 19 Feb 2010
Posts: 70

If a = b is a + b > ab ? [#permalink]
Show Tags
Updated on: 27 Mar 2018, 00:54
1
This post received KUDOS
16
This post was BOOKMARKED
Question Stats:
17% (01:34) correct 83% (01:13) wrong based on 447 sessions
HideShow timer Statistics
If a = b is a + b > ab ? (1) a = b (2) a = 3 I believe its B but the MR says its D. Attachment:
maths.jpg [ 99.43 KiB  Viewed 6019 times ]
Official Answer and Stats are available only to registered users. Register/ Login.
_________________
Yogesh Agarwal yogeshagarwala@gmail.com
CONSIDER AWARDING KUDOS IF MY POST HELPS !!!
Originally posted by yogeshagarwala on 13 Jul 2010, 14:59.
Last edited by Bunuel on 27 Mar 2018, 00:54, edited 2 times in total.
Edited the question.



SVP
Status: Three Down.
Joined: 09 Jun 2010
Posts: 1870
Concentration: General Management, Nonprofit

Re: If a = b is a + b > ab ? [#permalink]
Show Tags
13 Jul 2010, 15:10
1
This post received KUDOS
Given: \(a = b\)
To find: \(Is a+b>ab\)
Statement 1: \(a = b\)  Sufficient
\(=> a+b = 0\)
\(ab = (b)(b) = b^2 < 0\)
\(0 > ab\) since ab is negative.
Statement 2: \(a = 3\)  Sufficient
\(b = 3 = 3\)
\(=> a+b = 0\)
\(ab = (3)(3) = 9 < 0\)
\(0 > ab\) since ab is negative.
So the answer is D.



Math Expert
Joined: 02 Sep 2009
Posts: 44588

If a = b is a + b > ab ? [#permalink]
Show Tags
13 Jul 2010, 15:16
7
This post received KUDOS
Expert's post
3
This post was BOOKMARKED



Senior Manager
Joined: 25 Feb 2010
Posts: 409

Re: If a = b is a + b > ab ? [#permalink]
Show Tags
13 Jul 2010, 20:32
1
This post received KUDOS
Waoo I even came with D, but after looking to "Bunuel" post; I'm not sure what's wrong ?
_________________
GGG (Gym / GMAT / Girl)  Be Serious
Its your duty to post OA afterwards; some one must be waiting for that...



Manager
Status: one more time
Joined: 05 Jul 2010
Posts: 66
Location: United States
Concentration: Strategy, Entrepreneurship
GMAT 1: 700 Q49 V37 GMAT 2: 740 Q50 V40
GPA: 3.48
WE: Web Development (Computer Software)

Re: If a = b is a + b > ab ? [#permalink]
Show Tags
13 Jul 2010, 22:46
I think it is D.
Lets take statement 1, a = b.
Put that value in the equation a+b >ab then (b) +b > (b) (b) i.e. 0> b^2 As b^2 is always +ve this equaliton will hold true. Hence statement 1 is sufficient.
As above explanations say statement B is also sufficient.
B is answer.



Intern
Joined: 11 Oct 2009
Posts: 24

Re: If a = b is a + b > ab ? [#permalink]
Show Tags
14 Jul 2010, 02:31
Hi Yogesh .. can you please share the access codes for these tests. It will be very nice of you. My email id is sandeepuc@gmail.com. Thanks in advance.



Manager
Joined: 19 Feb 2010
Posts: 70

Re: If a = b is a + b > ab ? [#permalink]
Show Tags
14 Jul 2010, 08:47
Bunuel wrote: yogeshagarwala wrote: Please solve:
I believe its B but the MR says its D. If \(a=b\) is \(a+b>ab\)? First of all as \(a=b\) (\(b\) equals to absolute value of some number) then \(b\geq{0}\), as absolute value is always nonnegative. (1) \(a=b\) (\(b=a\)) > so \(a\leq{0}\) and \(LHS=a+b=0\). But \(RHS=ab\leq{0}\) thus we can not say for sure that \(a+b>ab\), because if \(a=b=0\) then \(a+b=0=ab\) (so in case \(a=b=0\), \(a+b\) is not more than \(ab\) it equals to \(ab\)). Not sufficient. (2) \(a=3\) > \(b=3\) > \(a+b=0>ab=9\). Sufficient. Answer: B. Hope it's clear. Bravo. This is the very reason I marked B but was shocked to see that MR people had marked it as D. Thanks Bunuel. You made my day.
_________________
Yogesh Agarwal yogeshagarwala@gmail.com
CONSIDER AWARDING KUDOS IF MY POST HELPS !!!



Current Student
Joined: 31 Mar 2010
Posts: 166
Schools: Tuck Class of 2013

Re: If a = b is a + b > ab ? [#permalink]
Show Tags
14 Jul 2010, 08:56
yogeshagarwala wrote: Bunuel wrote: yogeshagarwala wrote: Please solve:
I believe its B but the MR says its D. If \(a=b\) is \(a+b>ab\)? First of all as \(a=b\) (\(b\) equals to absolute value of some number) then \(b\geq{0}\), as absolute value is always nonnegative. (1) \(a=b\) (\(b=a\)) > so \(a\leq{0}\) and \(LHS=a+b=0\). But \(RHS=ab\leq{0}\) thus we can not say for sure that \(a+b>ab\), because if \(a=b=0\) then \(a+b=0=ab\) (so in case \(a=b=0\), \(a+b\) is not more than \(ab\) it equals to \(ab\)). Not sufficient. (2) \(a=3\) > \(b=3\) > \(a+b=0>ab=9\). Sufficient. Answer: B. Hope it's clear. Bravo. This is the very reason I marked B but was shocked to see that MR people had marked it as D. Thanks Bunuel. You made my day. So the trick here is not to consider zero. Probably the owner of the question forgot to say "a and b are both nonzero integers".



Intern
Joined: 06 Sep 2010
Posts: 36

Re: If a = b is a + b > ab ? [#permalink]
Show Tags
22 Apr 2011, 02:34
Oops what a catch !! Even I missed the 0.



Intern
Joined: 05 Mar 2013
Posts: 4

Re: If a = b is a + b > ab ? [#permalink]
Show Tags
26 Apr 2013, 06:55
Bunuel wrote: yogeshagarwala wrote: Please solve:
I believe its B but the MR says its D. If \(a=b\) is \(a+b>ab\)? First of all as \(a=b\) (\(b\) equals to absolute value of some number) then \(b\geq{0}\), as absolute value is always nonnegative. (1) \(a=b\) (\(b=a\)) > so \(a\leq{0}\) and \(LHS=a+b=0\). But \(RHS=ab\leq{0}\) thus we can not say for sure that \(a+b>ab\), because if \(a=b=0\) then \(a+b=0=ab\) (so in case \(a=b=0\), \(a+b\) is not more than \(ab\) it equals to \(ab\)). Not sufficient. (2) \(a=3\) > \(b=3\) > \(a+b=0>ab=9\). Sufficient. Answer: B. Hope it's clear. Thanks for the solution. But I still couldnt understand why are we taking a=0 and b=0 in the 1 st statement. It states a=b, is it ok to write 0=0..... It would be of great help if you can explain. It will help in clearing my doubts. Thanks in advance



Math Expert
Joined: 02 Sep 2009
Posts: 44588

Re: If a = b is a + b > ab ? [#permalink]
Show Tags
26 Apr 2013, 07:48
Richa16 wrote: Bunuel wrote: yogeshagarwala wrote: Please solve:
I believe its B but the MR says its D. If \(a=b\) is \(a+b>ab\)? First of all as \(a=b\) (\(b\) equals to absolute value of some number) then \(b\geq{0}\), as absolute value is always nonnegative. (1) \(a=b\) (\(b=a\)) > so \(a\leq{0}\) and \(LHS=a+b=0\). But \(RHS=ab\leq{0}\) thus we can not say for sure that \(a+b>ab\), because if \(a=b=0\) then \(a+b=0=ab\) (so in case \(a=b=0\), \(a+b\) is not more than \(ab\) it equals to \(ab\)). Not sufficient. (2) \(a=3\) > \(b=3\) > \(a+b=0>ab=9\). Sufficient. Answer: B. Hope it's clear. Thanks for the solution. But I still couldnt understand why are we taking a=0 and b=0 in the 1 st statement. It states a=b, is it ok to write 0=0..... It would be of great help if you can explain. It will help in clearing my doubts. Thanks in advance Yes, it's ok to write 0=0.
_________________
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



Senior Manager
Joined: 13 May 2013
Posts: 431

Re: If a = b is a + b > ab ? [#permalink]
Show Tags
25 Jun 2013, 16:33
1
This post was BOOKMARKED
If a = b is a + b > ab
(1) a = b (2) a = 3
a = b so b MUST be ≥ 0
1.) a = b b=a
So what do we know?
a=b b is positive a is the negative value of b
So, a + b > ab a+b = 0 HOWEVER we are not sure what values a and b are. For example, a and b could be 3 and 3 or a and b could be 0 and 0. INSUFFICIENT
(2) a = 3 We know that a=b, so if a = 3 then b must = 3 a + b > ab 3+3 > (3)(3) 0>9 TRUE
Answer = b



Intern
Joined: 03 Apr 2016
Posts: 15

Re: If a = b is a + b > ab ? [#permalink]
Show Tags
02 Jun 2016, 05:20
please change the ans to b in oa.



NonHuman User
Joined: 09 Sep 2013
Posts: 6641

Re: If a = b is a + b > ab ? [#permalink]
Show Tags
27 Mar 2018, 00:22
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 Books  GMAT Club Tests  Best Prices on GMAT Courses  GMAT Mobile App  Math Resources  Verbal Resources




Re: If a = b is a + b > ab ?
[#permalink]
27 Mar 2018, 00:22






