|
Author |
Message |
|
Intern
Joined: 27 Oct 2010
Posts: 10
Followers: 0
Kudos [?]:
1
[0], given: 8
|
Thanks Bunuel for the wonderful explanation , now i realise where i was wrong .
Thanks & Regards,
BLUEMINT
|
|
|
|
|
|
|
Math Forum Moderator
Joined: 20 Dec 2010
Posts: 2100
Followers: 108
Kudos [?]:
654
[0], given: 376
|
Re: Data Sufficiency - Simultaneous Equations [#permalink]
 12 Apr 2011, 09:32
amp0201 wrote: Is the product of A and B equal to 1?
1. A * B * A = A
2. B * A * B = B
1. Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient
2. Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient
3. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient
4. EACH statement ALONE is sufficient
5. Statements (1) and (2) TOGETHER are NOT sufficient
Please justify your answer, as I am not sure if the OA is correct. Thanks. 1. A^2B-A=0A(AB-1)=0Either A=0 OR AB=1 If A=0; AB=0 OR AB=1 AB can be 0 or 1. Not Sufficient. 2. B^2A-B=0B(AB-1)=0Either B=0 OR AB=1 If B=0; AB=0 OR AB=1 AB can be 0 or 1. Not Sufficient. Combining both statements: Either A and B are both 0 OR AB=1 If A and B are both zeros: AB=0 or AB=1 Not Sufficient. Ans: "E"
_________________
~fluke
Find out what's new at GMAT Club - latest features and updates
|
|
|
|
|
|
Manager
Joined: 24 Dec 2009
Posts: 229
Followers: 2
Kudos [?]:
19
[0], given: 3
|
Re: Data Sufficiency - Simultaneous Equations [#permalink]
12 Apr 2011, 09:42
How can AB can be 0 or 1 ?
in (1) - A= 0 or AB =1 and (2) B = 0 or AB = 1 so combining (1) & (2) => can't we say AB=1 and hence C.
|
|
|
|
|
|
Math Forum Moderator
Joined: 20 Dec 2010
Posts: 2100
Followers: 108
Kudos [?]:
654
[0], given: 376
|
Re: Data Sufficiency - Simultaneous Equations [#permalink]
12 Apr 2011, 09:46
amp0201 wrote: How can AB can be 0 or 1 ?
in (1) - A= 0 or AB =1 and (2) B = 0 or AB = 1 so combining (1) & (2) => can't we say AB=1 and hence C. Is the product of A and B equal to 1? 1. A * B * A = A 2. B * A * B = B ************************* Substitution: A=0, B=0 A * B * A = A 0*0*0=0 True B * A * B = B 0*0*0=0 True. A=1, B=1 A * B * A = A 1*1*1=1 True B * A * B = B 1*1*1=1 True. Makes more sense now?
_________________
~fluke
Find out what's new at GMAT Club - latest features and updates
|
|
|
|
|
|
SVP
Joined: 16 Nov 2010
Posts: 1717
Location: United States (IN)
Concentration: Strategy, Technology
Followers: 26
Kudos [?]:
227
[0], given: 34
|
Re: Data Sufficiency - Simultaneous Equations [#permalink]
12 Apr 2011, 19:06
1. A * B * A = A => A(AB -1) = 0 => A = 0 or AB = 1, so not sufficient 2. B * A * B = B => B(AB-1) = 0 => B = 0 or AB = 1, so not sufficient (1) and (2) combined says that A = 0, or B = 0 or AB = 1 Which can mean that either AB = 0, or AB = 1 Not sufficient Answer - E
_________________
Formula of Life -> Achievement/Potential = k * Happiness (where k is a constant)
Find out what's new at GMAT Club - latest features and updates
|
|
|
|
|
|
Director
Joined: 01 Feb 2011
Posts: 792
Followers: 11
Kudos [?]:
62
[0], given: 42
|
Re: Data Sufficiency - Simultaneous Equations [#permalink]
14 Apr 2011, 05:52
1. Not sufficient. A=0 or AB=1 2. Not sufficient. B=0 or AB = 1 Together we have A=0,B=0 or AB=1. Still not sufficient. Answer is E. Posted from my mobile device 
|
|
|
|
|
|
Manager
Affiliations: University of Tehran
Joined: 06 Feb 2011
Posts: 204
Location: Iran (Islamic Republic of)
Grad GPA: 4
Concentration: Marketing
GMAT 1: 680 Q45 V38
GPA: 4
WE: Marketing (Retail)
Followers: 5
Kudos [?]:
32
[0], given: 57
|
dzyubam wrote: It's not a good practice to divide the parts of an equation by the unknown (A or B here) because this unknown can be 0. As we know, division by 0 can't be done. jainanurag78 wrote: I think it should be D. Why can we divide A*B*A=A by A on both the sides and it would give us AB =1 same with the S2. Ok, we can try it, but just like absolute values, we have to consider two scenarios: 1) A is NOT equal to 0 : Well here AB=1 2) A is EQUAL to zero. Here since we can not divide, we have to find other ways to manipulate the statements. We arrive at A(AB-1)=0. Analyzing it, we can see AB can be both 1 and 0. Insuf. I think D is irrelevant and if we are gonna become dubious b/w two choices, they are more likely to be C and E. As you know the general guideline is to choose C b/w C and E on tough questions when it comes to guessing. Solving it, I couldn't make my brain free of the thought that the statements together may be suf.
_________________
Ambition, Motivation and Determination: the three "tion"s that lead to PERFECTION.
World! Respect Iran and Iranians as they respect you! Leave the governments with their own.
|
|
|
|
|
|
Intern
Joined: 05 Jul 2011
Posts: 5
Followers: 0
Kudos [?]:
0
[0], given: 0
|
answer is definitely C)
1) A=0 or AB=1
2) B=0 or AB=1
C) AB=1 is the only solution that satisfies both statements --> Does AB=1? --> YES
|
|
|
|
|
|
Intern
Joined: 05 Jul 2011
Posts: 5
Followers: 0
Kudos [?]:
0
[0], given: 0
|
E)
1) A=0 (meaning AB=0) OR AB=1
2) B=0 (meaning AB=0) OR AB=1
Yes, E) is the correct answer. Even putting the two statements together, there are two possibilities for the value of AB (0 OR 1)
|
|
|
|
|
|
Intern
Joined: 18 Jan 2012
Posts: 46
Location: United States
Followers: 1
Kudos [?]:
36
[0], given: 21
|
What are wonderful question ! Reminds me of the Mona lisa.. Wonderfully simple in its presentation, yet on closer inspection, the painting reveals so many subtleities. Anyway, the key point to remember is that , on the GMAT, a) If the questions pertains to the "=" symbol, never ever cancel terms on both ends unless one is sure that the variable is not equal to 0. Remember that there is no such mathematical action as "Cancellation". Cancellation is division in disguise. b) If the question pertains to the ">" or "<" symbol, never ever divide, or cross multiply unless one is certain that the variable being acted upon is >0. Remember that there is no such mathematical operation as "Cross multiplying". It is multiplication in disguise Apply the FOIN tests to ensure that you have covered all the values that a variable may assume :- F - Fraction o - ZERO i - Integer or Irrational N - Negative
_________________
-----------------------------------------------------------------------------------------------------
IT TAKES QUITE A BIT OF TIME AND TO POST DETAILED RESPONSES.
YOUR KUDOS IS VERY MUCH APPRECIATED
-----------------------------------------------------------------------------------------------------
|
|
|
|
|
|
Intern
Joined: 26 Jul 2012
Posts: 2
Followers: 0
Kudos [?]:
0
[0], given: 0
|
well, i first chose E but on a second thought, i chose A , cos, drug related is an entity and others' is another entity that must be recognised as well. so i go for A, i hope am right.
|
|
|
|
|
|
GMAT Club team member
Joined: 02 Sep 2009
Posts: 11506
Followers: 1791
Kudos [?]:
9526
[0], given: 826
|
|
|
|
|
|
|
Intern
Joined: 06 Mar 2012
Posts: 14
Followers: 0
Kudos [?]:
0
[0], given: 8
|
when you take it combined, you say:
either (A=0 and B=0) or (AB=1) ----not sufficient.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
close
