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Does (a – 2)(b + 4) = 8?
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20 Jan 2019, 21:45
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58% (01:38) correct 42% (01:44) wrong based on 57 sessions
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Does (a – 2)(b + 4) = 8? (1) ab = 2b – 4a (2) a = 6 Source Kaplan Mock Test
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Re: Does (a – 2)(b + 4) = 8?
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20 Jan 2019, 21:59
(a – 2)(b + 4) = ab + 4a 2b  8 (1) ab = 2b – 4a ab+4a  2b=0 Hence (a – 2)(b + 4) = ab + 4a 2b  8 = 0 8 = 8 Sufficient (2) a = 6 (a – 2)(b + 4) = 4(b+4) Without the value of b  Insufficient A
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Does (a – 2)(b + 4) = 8?
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Updated on: 21 Jan 2019, 02:40
divyadamahe wrote: Does (a – 2)(b + 4) = 8? (1) ab = 2b – 4a (2) a = 6 Source Kaplan Mock Test Does (a – 2)(b + 4) = 8 (a) Statement 1 ab = 2b  4a (a) becomes ab + 4a  2b  8 = 8 2b  4a + 4a 2b = 16 0 != 16 Sufficient Statement 2, a = 6 Though if i substitute this in the question, I can calculate the value of b as  2, But question has asked us does (a – 2)(b + 4) = 8, is LHS = RHS 4b + 16 = 8, so now b could have been a fraction, integer or a real number. Without the value of b we cannot tell that, Hence insufficient Answer A
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Originally posted by KanishkM on 20 Jan 2019, 22:16.
Last edited by KanishkM on 21 Jan 2019, 02:40, edited 1 time in total.



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Re: Does (a – 2)(b + 4) = 8?
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21 Jan 2019, 02:18
KanishkM wrote: divyadamahe wrote: Does (a – 2)(b + 4) = 8? (1) ab = 2b – 4a (2) a = 6 Source Kaplan Mock Test Does (a – 2)(b + 4) = 8 (a) Statement 1 ab = 2b  4a (a) becomes ab + 4a  2b  8 = 8 2b  4a + 4a 2b = 16 0 != 16 Sufficient Statement 2, a = 6 Though if i substitute this in the question, I can calculate the value of b as  2, But b can be an integer, a number or a real number Not sufficient Answer A Hi dude, Can you explain to me your reasoning? If b equals 2; why am I suppose to say that the solution is not correct? Thank you very much!!!!



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Re: Does (a – 2)(b + 4) = 8?
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21 Jan 2019, 02:35
oblivion441 wrote: KanishkM wrote: divyadamahe wrote: Does (a – 2)(b + 4) = 8? (1) ab = 2b – 4a (2) a = 6 Source Kaplan Mock Test Does (a – 2)(b + 4) = 8 (a) Statement 1 ab = 2b  4a (a) becomes ab + 4a  2b  8 = 8 2b  4a + 4a 2b = 16 0 != 16 Sufficient Statement 2, a = 6 Though if i substitute this in the question, I can calculate the value of b as  2, But b can be an integer, a number or a real number Not sufficient Answer A Hi dude, Can you explain to me your reasoning? If b equals 2; why am I suppose to say that the solution is not correct? Thank you very much!!!! I had the same question when i solved this question, but later i realized that the question was never 1) to find the value of b, 2) then prove that the question stem is true or not. IMO it was like is LHS = RHS, i should like edit my explanation a bit
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Re: Does (a – 2)(b + 4) = 8?
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21 Jan 2019, 02:41
KanishkM wrote: I had the same question when i solved this question, but later i realized that the question was never 1) to find the value of b, 2) then prove that the question stem is true or not. IMO it was like is LHS = RHS, i should like edit my explanation a bit I understand your point. But if I know that a= 6 and so b=2 I can answer the question (a – 2)(b + 4) = 8 The only thing that comes in my mind is that we are getting to different results, and this is usually impossible in DS questions. But I still don't get why b=2 is not correct.



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Re: Does (a – 2)(b + 4) = 8?
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21 Jan 2019, 02:46
oblivion441 wrote: KanishkM wrote: I had the same question when i solved this question, but later i realized that the question was never 1) to find the value of b, 2) then prove that the question stem is true or not. IMO it was like is LHS = RHS, i should like edit my explanation a bit I understand your point. But if I know that a= 6 and so b=2 I can answer the question (a – 2)(b + 4) = 8 The only thing that comes in my mind is that we are getting to different results, and this is usually impossible in DS questions. But I still don't get why b=2 is not correct. No worries, I am glad that b = 2, stirred some questions for someone, Nevertheless lets wait for the gc community to reply. 4d, What is your take at this ? Can you also share your insight on this ??
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Re: Does (a – 2)(b + 4) = 8?
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21 Jan 2019, 02:49
oblivion441 wrote: KanishkM wrote: I had the same question when i solved this question, but later i realized that the question was never 1) to find the value of b, 2) then prove that the question stem is true or not. IMO it was like is LHS = RHS, i should like edit my explanation a bit I understand your point. But if I know that a= 6 and so b=2 I can answer the question (a – 2)(b + 4) = 8 The only thing that comes in my mind is that we are getting to different results, and this is usually impossible in DS questions. But I still don't get why b=2 is not correct. b = 2 is not correct because from (2) we don't get that b = 2. THE QUESTION BECOMES: does b = 2? Notice that we are NOT given that (a – 2)(b + 4) = 8. We are asked to answer this. Does (a – 2)(b + 4) = 8?Does ab + 4a  2b = 16? (1) ab = 2b – 4a > ab + 4a  2b = 0. So, the answer to the question is NO: ab + 4a  2b equals to 0 not 16. Sufficient. (2) a = 6. The question becomes: does b = 2? We don't know that. Not sufficient. Answer: A.
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Re: Does (a – 2)(b + 4) = 8?
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21 Jan 2019, 03:08
KanishkM oblivion441The question is Does (a – 2)(b + 4) = 8?Now when a = 6 Is 4(b+4)=8 ? If b=2 , its 8  YESIf is any other number  NOIn any DS question if you have YES and NO as your answer . Then the data is insufficient . That means using a=6 , i cannot say whether (a – 2)(b + 4) = 8 or not Hence insufficient
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Re: Does (a – 2)(b + 4) = 8?
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21 Jan 2019, 06:12
4d wrote: KanishkM oblivion441The question is Does (a – 2)(b + 4) = 8?Now when a = 6 Is 4(b+4)=8 ? If b=2 , its 8  YESIf is any other number  NOIn any DS question if you have YES and NO as your answer . Then the data is insufficient . That means using a=6 , i cannot say whether (a – 2)(b + 4) = 8 or not Hence insufficient Thanks dude, I got it!




Re: Does (a – 2)(b + 4) = 8?
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