a,b,c integers

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kalpanas: Newbie | Next Rank: 10 Posts; Posts: 2; Joined: Fri Jan 13, 2012 10:49 am

by kalpanas » Sat Feb 04, 2012 5:21 am

Example: If a, b and c are integers and a.b + c is odd, what is true?
I. a + c is odd
II. b + c is odd
III. a.b.c is even
The answer provided for this is III.is this right?

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Source: Beat The GMAT — Problem Solving | Sat Feb 04, 2012 5:21 am

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Anurag@Gurome: GMAT Instructor; Posts: 3835; Joined: Fri Apr 02, 2010 10:00 pmFollowed by: 523 members; Location: Milpitas, CA; Thanked: 1854 times; GMAT Score:770

by Anurag@Gurome » Sat Feb 04, 2012 5:49 am

kalpanas wrote:Example: If a, b and c are integers and a.b + c is odd, what is true?
I. a + c is odd
II. b + c is odd
III. a.b.c is even
The answer provided for this is III.is this right?

ab + c = odd implies

Case 1: ab = even, c = odd
If a = even, b = even, then a + c = even + odd = odd, b + c = even + odd = odd, abc = even
If a = odd, b = even, then a + c = odd + odd = even, b + c = even + odd = odd, abc = even
If a = even, b = odd, then a + c = even + odd = odd, b + c = odd + odd = even, abc = even

Case 2: ab = odd, c = even
If a = odd, b = odd, then a + c = odd + odd = even, b + c = odd + even = odd, abc = even

It can be seen that abc = even in all the cases.

The correct answer is III.

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pappueshwar: Master | Next Rank: 500 Posts; Posts: 234; Joined: Fri Oct 01, 2010 7:28 pmFollowed by: 4 members; Location: chennai; Thanked: 5 times

by pappueshwar » Sun Feb 05, 2012 9:48 am

hi anurag,

wats the final answer ? is it III ?

THE ANSWERS are getting covered by a dark spot, its very confusing in most of your solutions since i am solving the problem with out seeing your solution and checking if i am right or not.

request to remove the same so as to clear the ambiguity while posting the answer. is this dark spot a some system generated one ?

thanks
eshwar

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Anurag@Gurome: GMAT Instructor; Posts: 3835; Joined: Fri Apr 02, 2010 10:00 pmFollowed by: 523 members; Location: Milpitas, CA; Thanked: 1854 times; GMAT Score:770

by Anurag@Gurome » Sun Feb 05, 2012 5:34 pm

pappueshwar wrote:hi anurag,

wats the final answer ? is it III ?

THE ANSWERS are getting covered by a dark spot, its very confusing in most of your solutions since i am solving the problem with out seeing your solution and checking if i am right or not.

request to remove the same so as to clear the ambiguity while posting the answer. is this dark spot a some system generated one ?

thanks
eshwar

Hi Eshwar!
Yes the correct answer is III. The black spot is the spoiler, and it's always better to hide the answer by using spoiler in my view.
Thanks,

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