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For integers a and b, is the expression ab – b even? https://gmatclub.com/forum/forintegersaandbistheexpressionabbeven242106.html 
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Author:  Bunuel [ 06 Jun 2017, 11:42 ] 
Post subject:  For integers a and b, is the expression ab – b even? 
For integers a and b, is the expression ab – b even? (1) a is odd (2) b is odd 
Author:  BrentGMATPrepNow [ 06 Jun 2017, 11:55 ] 
Post subject:  Re: For integers a and b, is the expression ab – b even? 
Bunuel wrote: For integers a and b, is the expression ab – b even? (1) a is odd (2) b is odd Target question: Is the expression ab – b even? HINT: notice that ab – b = b(a  1) Statement 1: a is odd What does does this tell us about the expression ab – b? Well, ab – b = b(a  1) = b(ODD  1) = b(EVEN) [since an odd integer minus 1 gives us a EVEN integer] = EVEN Since we can answer the target question with certainty, statement 1 is SUFFICIENT Statement 2: b is odd There are several values of a and b that satisfy statement 2. Here are two: Case a: a = 3 and b = 1. In this case ab – b = (3)(1)  1 = 2. So, ab – b is EVEN Case b: a = 2 and b = 1. In this case ab – b = (2)(1)  1 = 1. So, ab – b is ODD Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT Answer: Cheers, Brent 
Author:  Gnpth [ 25 Jul 2017, 17:49 ] 
Post subject:  Re: For integers a and b, is the expression ab – b even? 
abb can be converted into b(a1), We have to find either b or a1 to be even. st1 says a is odd. then a1 is even. So the term b(a1) will be even. sufficient. st2 says b is odd. No info about a. so not sufficient. Answer is A. 
Author:  ocelot22 [ 16 Jan 2019, 13:20 ] 
Post subject:  Re: For integers a and b, is the expression ab – b even? 
Bunuel wrote: For integers a and b, is the expression ab – b even? (1) a is odd (2) b is odd b(a1) even? (1) a odd, then a1 is even, then we have even *b = even sufficient (2) b odd. Let be =1 1(a1) even? let a=1. Then abb = 1(0) = 0 Yes even. Let a=2 then abb 1(21) =1 No. Odd. NS Answer is A 
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Post subject:  Re: For integers a and b, is the expression ab b even? 
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