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If a and b are integers and ab − a is odd, which of the following must
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10 May 2017, 12:08
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If a and b are integers and ab − a is odd, which of the following must be odd? (A) b^2 (B) b (C) a^2 + b (D) ab (E) ab + b
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Re: If a and b are integers and ab − a is odd, which of the following must
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10 May 2017, 12:36
Bunuel wrote: If a and b are integers and ab − a is odd, which of the following must be odd?
(A) b^2 (B) b (C) a^2 + b (D) ab (E) ab + b b has to even for aba to be odd. Answer is C



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Re: If a and b are integers and ab − a is odd, which of the following must
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10 May 2017, 18:54
If a and b are integers and ab − a is odd...
then a(b1) is odd
then a and (b1) are odds
then b= (b1)+1 is even
so we have i) a odd ii) b even
which of the following must be odd?
(A) b^2 evenxeven=even NOT (B) b even NOT (C) a^2 + b = oddxpdd + even = odd + even = odd YES (D) ab = oddxeven = even NOT (E) ab + b oddxeven + even = even + even = even NOT



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Re: If a and b are integers and ab − a is odd, which of the following must
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11 May 2017, 04:59
there can be two scenarios,, if a is odd, b is even,,,or vice versa...
hece C fits in,,,,ans C



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Re: If a and b are integers and ab − a is odd, which of the following must
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11 May 2017, 05:19
Bunuel wrote: If a and b are integers and ab − a is odd, which of the following must be odd?
(A) b^2 (B) b (C) a^2 + b (D) ab (E) ab + b a,b E Integer aba is odd. Now ab  a can be odd  even or even  odd for the total value to be odd. Case 1 : a is odd To make ab even, b must be even. so {a= odd, b = even}. Case 2 : a is even But in this case ab can't be odd. so this case is not possible. So overall a = odd, b = even.(A) b^2 = even (B) b = even (C) a^2 + b = odd (D) ab = even (E) ab + b = even
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Re: If a and b are integers and ab − a is odd, which of the following must
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11 May 2017, 05:22
mohshu wrote: there can be two scenarios,, if a is odd, b is even,,,or vice versa...
hece C fits in,,,,ans C Only one scenario is there right?? Given a and b are integers. For ab − a to be odd a>odd b>even square of an odd integer is odd ,adding an even number will give odd number hence C if b is odd and a is even then aba will be even.
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Re: If a and b are integers and ab − a is odd, which of the following must
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11 May 2017, 09:08
VyshakhR1995 wrote: mohshu wrote: there can be two scenarios,, if a is odd, b is even,,,or vice versa...
hece C fits in,,,,ans C Only one scenario is there right?? Given a and b are integers. For ab − a to be odd a>odd b>even square of an odd integer is odd ,adding an even number will give odd number hence C if b is odd and a is even then aba will be even. Yes, if ab  a is odd, one of ab and a must be odd and the other even. If a is even, then ab must be even too. Hence a must be odd only. To make ab even, then b must be even. There is only one scenario: a odd and b even
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Re: If a and b are integers and ab − a is odd, which of the following must
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15 May 2017, 17:25
Bunuel wrote: If a and b are integers and ab − a is odd, which of the following must be odd?
(A) b^2 (B) b (C) a^2 + b (D) ab (E) ab + b We can simplify the given expression: a(b  1) = odd Since odd x odd = odd, we see that a has to be odd and b  1 has to be odd, which means b must be even. Since even + odd (or odd + even) = odd, we see that a^2 + b must be odd: a^2 = odd^2 = odd number b = even number Thus, odd + even = odd. Answer: C
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Re: If a and b are integers and ab − a is odd, which of the following must
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17 Aug 2018, 18:24
If a and b are integers and ab − a is odd, which of the following must be odd?
(A) b^2 (B) b (C) a^2 + b (D) ab (E) ab + b
aba is O
O*O=O O+/E = O
so, either ab = even and a is odd. In that case b is even or ab = odd and a is even. Not possible (if a is even ab has to be even)
only, C a^2+b is O+O = O



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Re: If a and b are integers and ab − a is odd, which of the following must
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17 Aug 2018, 18:39
As aba is odd It means either ab is odd or a is odd. Both can’t be even or odd. If a is odd and b is even then ab is even and whole expression will be odd. If b is odd and a is even then ab will be even and whole expression will be even which is not true according to statement. So a must be odd and b must be even. Now lets look at answers: A) B^2 even B) b even C) a^2 + b odd + even = odd D) ab even E) ab + b even So answer is (C) Posted from my mobile device
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Re: If a and b are integers and ab − a is odd, which of the following must
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