GMATPrep Question 28

gurudev · Posted: Thu Sep 04, 2008 12:27 pm Post subject: GMATPrep Question 28

If m and n are integers, Is m odd?

1. n+m is odd.
2. n+m=n^2+5

Please help me on the above question, as i am not able to get the logic behind this!!

bourne159 · Posted: Thu Sep 04, 2008 2:37 pm Post subject:

You can solve this by picking some numbers.

Choice 1:
n + m is odd
Sum of two integers is odd only if one of the numbers is odd and the other is even. So you can see that is the case n is even m has to be odd and in the case where n is odd m has to be even.
So 1 is not sufficient to answer if m is odd.

You can just pick numbers:
pick an odd value for n (say 3) and then m has to be even(say 4) to make the sum odd (7)
Similarly you can interchange values and see that if n is even (4) then m has to be odd (3) to make the sum odd (7)

Choice 2:
n + m = n^2 + 5
Pick an odd value for n in one example and an even value in the other.
See what happens to m.

Let's say n is 4(even) then 4 + m = 16 + 5, m = 17 (odd)
Now pick a odd value for n (say 5) then 5 + m = 25 + 5, m = 25 (odd)

So 2 is sufficient condition to say that m is odd.

The answer is B

Stuart Kovinsky · Posted: Thu Sep 04, 2008 2:42 pm Post subject: Re: GMATPrep Question 28

gurudev · Posted: Thu Sep 04, 2008 11:56 pm Post subject:

Yeah Got it now!!!!

Thanks a ton..