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Manager
Joined: 01 Apr 2006
Posts: 185
Location: Toronto, Canada
Followers: 1
Kudos [?]:
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Question Stats:
75% (01:43) correct
25% (00:18) wrong based on 1 sessions
a , b , and c are integers. Is abc = 0 ? 1. a^2 = 2a2. \frac{b}{c} = \frac{(a+b)^2}{a^2+2ab+b^2} - 1 ( a \ne -b and c \ne 0 ) Source: GMAT Club Tests - hardest GMAT questions Can't seem to figure out the explanation that I saw on the test. Thanks, John.
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Manager
Joined: 01 Apr 2006
Posts: 185
Location: Toronto, Canada
Followers: 1
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Can anyone help? 
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CIO
Joined: 02 Oct 2007
Posts: 1261
Followers: 75
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Hi. From S1 we see that a is either 0 or 2. Insufficient. S2. You have to notice that we need to simplify the fraction in S2: \frac{b}{c} = \frac{(a+b)^2}{a^2+2ab+b^2} - 1\frac{b}{c} = \frac{(a+b)^2}{(a+b)^2} - 1\frac{b}{c} = 1 - 1 = 0b = 0Hope this helps.
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Manager
Joined: 12 Feb 2008
Posts: 186
Followers: 1
Kudos [?]:
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dzyubam wrote: Hi.
From S1 we see that a is either 0 or 2. Insufficient.
S2. You have to notice that we need to simplify the fraction in S2:
\frac{b}{c} = \frac{(a+b)^2}{a^2+2ab+b^2} - 1
\frac{b}{c} = \frac{(a+b)^2}{(a+b)^2} - 1
\frac{b}{c} = 1 - 1 = 0
b = 0
Hope this helps. he is missing -1 in S2. otherwise good one dzyubam
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Manager
Joined: 17 Apr 2010
Posts: 115
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Kudos [?]:
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The answer is B right?
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Intern
Joined: 14 Dec 2009
Posts: 12
Followers: 0
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Can some one explain Statement 1? Thanks!
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Intern
Joined: 26 Apr 2010
Posts: 5
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nshah12 wrote: Can some one explain Statement 1? Thanks! Statement one is saying that the square of A is equal to 2 x A. So this can be 2 or 0. 0 squared = 0 * 0 = 0 2 * 0 = 0 AND 2 squared = 2 * 2 = 4 2 * 2 = 4 So statement implies that A is either 0 or 2, therefore we can't tell if ABC = 0. Hope that helps.
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CIO
Joined: 02 Oct 2007
Posts: 1261
Followers: 75
Kudos [?]:
506
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Yes you're right. You can see the OA in the spoiler after clicking "Reveal". tiruraju wrote: The answer is B right?
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Manager
Joined: 04 Feb 2010
Posts: 67
Schools: IESE '13
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B for the reasons already stated.
b^2 + 2bc + c^2 = (b + c)^2
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Manager
Joined: 15 Apr 2010
Posts: 200
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Kudos [?]:
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this is how I approached it:
1) First condition gives us 2 possible values of a => a=0 or 2
2) Second condition comes as [b][/c] = 1-1=0
since "c" is not = 0, "b" is zero to make the result "0". hence B is the answer!
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Manager
Joined: 15 Sep 2009
Posts: 149
Followers: 1
Kudos [?]:
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I will go with option B
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Intern
Joined: 17 May 2010
Posts: 25
Followers: 0
Kudos [?]:
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At first I forgot the value 0 of a in (1). Luckily it's correct to choose B. But should be careful next time.
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Intern
Joined: 11 Jan 2010
Posts: 32
Followers: 1
Kudos [?]:
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Question: Is abc = 0? Solution 1: a^2 = 2a => a . (a-2) = 0 => a = 0 or a = 2 When a = 0 => abc = 0 When a = 2 => abc may or may not be zeros depending on the values of b and c. Thus, solution 1 does not give a clear yes or no answer and is not sufficient. Solution 2: Solving the given equation: a^2 + 2ab + b^2 = (a + b)^2 Thus, b/c = 1 - 1 = 0 => b = 0 When b = 0 => abc = 0 Thus, Solution 2 gives a clear answer that, yes, abc = 0. Therefore, the correct answer choice is B. Award me with Kudos+1, if this helps!! Cheers!!!
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Director
Joined: 21 Dec 2009
Posts: 592
Concentration: Entrepreneurship, Finance
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Kudos [?]:
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Enough solution has been given from the previous posts. (1) a= 0 or 2...insufficient (2) b=0...sufficient to answer whether abc = 0 (yes). B, off course is the answer.
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Manager
Joined: 04 Dec 2009
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Location: INDIA
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Kudos [?]:
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S1 ,a=2 or 0 not sufficieant S2,B=0 so sufficieant
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Manager
Joined: 12 Jul 2010
Posts: 70
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Kudos [?]:
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Its B.
Only B gives a distinct value Zero.
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Manager
Joined: 27 May 2010
Posts: 205
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Kudos [?]:
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A is insufficient as a=2 and B & C values are not given
B is sufficient because b/c = 1-1 => 0
Since c cannot be zero, b = 0 ==> abc=0
Therefore answer is B
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Director
Joined: 01 Feb 2011
Posts: 792
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Kudos [?]:
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1. Not sufficient As a can be 0 or 2,abc may or may not be 0. 2.Sufficient b/c = 1-1 = 0. => b=0=> abc=0 Answer is B. Posted from my mobile device 
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Manager
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Yey! Correct! I answered B.
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Intern
Joined: 02 Nov 2010
Posts: 48
Followers: 0
Kudos [?]:
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It's B. Took me a minute to reread statement 2. Once I realized it stated C couldn't be 0 it became much clearer.
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