M N P

This topic has expert replies
Legendary Member
Posts: 2789
Joined: Tue Jul 26, 2011 12:19 am
Location: Chennai, India
Thanked: 206 times
Followed by:43 members
GMAT Score:640

M N P

by GmatKiss » Thu May 17, 2012 11:50 am
If m, n, and p are integers, is m + n odd?

(1) m = p^2 + 4p + 4

(2) n = p^2 + 2m + 1

User avatar
Community Manager
Posts: 1060
Joined: Fri May 13, 2011 6:46 am
Location: Utrecht, The Netherlands
Thanked: 318 times
Followed by:52 members

by neelgandham » Thu May 17, 2012 12:36 pm
If m, n, and p are integers, is m + n odd?
(1) m = p^2 + 4p + 4

No mention of n. So, Statement 1 is insufficient to answer the question.
(2) n = p^2 + 2m + 1
If p is an odd number and m is an odd number then n is an even number and m+n is an odd number
If p is an odd number and m is an even number then n is an even number and m+n is an even number.
We got two different answers. So, Statement 2 is Insufficient to answer the question.
1 + 2
Adding the left hand side and right hand side of both the statements, we get
m + n = 2*p^2 + 4p + 2m + 5 = 2*(p^2 + 2p + m) + 5 = 2X + 5( Where X is an Integer). So, m+n is always Odd.

IMO C
Anil Gandham
Welcome to BEATtheGMAT | Photography | Getting Started | BTG Community rules | MBA Watch
Check out GMAT Prep Now's online course at https://www.gmatprepnow.com/

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3835
Joined: Fri Apr 02, 2010 10:00 pm
Location: Milpitas, CA
Thanked: 1854 times
Followed by:523 members
GMAT Score:770

by Anurag@Gurome » Thu May 17, 2012 6:44 pm
GmatKiss wrote:If m, n, and p are integers, is m + n odd?

(1) m = p^2 + 4p + 4

(2) n = p^2 + 2m + 1
(1) m = p² + 4p + 4 = (p + 2)²
Now m can be either even or odd, depending on p's value and nothing is given about n; NOT sufficient.

(2) n = p² + 2m + 1
Now 2m will always be even, whether m is even or odd
p² + 1 can be either even or odd, which depends on p's value.
So, nothing is definite about m's and n's value; NOT sufficient.

Combining (1) and (2), m + n = p² + 4p + 4 + p² + 2m + 1 = 2p² + 4p + 2m + 5 = even + odd = odd
So, m + n is always odd; SUFFICIENT.

The correct answer is C.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/

Junior | Next Rank: 30 Posts
Posts: 20
Joined: Mon Jun 04, 2012 4:49 pm
Thanked: 2 times

by minkathebest » Sat Sep 22, 2012 1:45 pm
Thank you!
Anurag@Gurome wrote:
GmatKiss wrote:If m, n, and p are integers, is m + n odd?

(1) m = p^2 + 4p + 4

(2) n = p^2 + 2m + 1
(1) m = p² + 4p + 4 = (p + 2)²
Now m can be either even or odd, depending on p's value and nothing is given about n; NOT sufficient.

(2) n = p² + 2m + 1
Now 2m will always be even, whether m is even or odd
p² + 1 can be either even or odd, which depends on p's value.
So, nothing is definite about m's and n's value; NOT sufficient.

Combining (1) and (2), m + n = p² + 4p + 4 + p² + 2m + 1 = 2p² + 4p + 2m + 5 = even + odd = odd
So, m + n is always odd; SUFFICIENT.

The correct answer is C.