number properties

This topic has expert replies
Source: — Data Sufficiency |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 273
Joined: Tue Sep 21, 2010 5:37 am
Location: Durham, NC
Thanked: 154 times
Followed by:74 members
GMAT Score:770

by Whitney Garner » Tue Jan 31, 2012 11:02 am
sud21 wrote:Image
Hi Sud21!

The easiest way to approach this problem is with a number line (well, 2 number lines actually).

We know that k and m are consecutive even numbers, but we don't know which is bigger. That means that we have one of the following 2 cases:

(a) <------- K ---- | ---- M --------> K is NOT larger than M (k<m)

(b) <------- M ---- | ---- K --------> K IS larger than M (k>m)

Now, all we need to do to answer the question is eliminate one of these 2 cases.

Statement (1)
tells us that (k+2) and (m-2) are no longer consecutive even integers...so let's apply this to both number lines and see:

(a) <------- M-2 ---- | ---- K+2 -------->
these are still consecutive, so this cannot be the true case

(b) <------- M-2 ---- | ---- M ---- | ---- K ---- | ---- K+2 -------->
M-2 and K+2 are NOT consecutive, so this must be the true case

Statement 1 is [spoiler]SUFFICIENT![/spoiler]


Statement (2)
tells us that (k-1) and (m+3) are consecutive odd integers...so let's apply this to both number lines and see:

(a) <------- (K-1) ---- K ---- | ---- M ---- | ---- | ---- (M+3) -------->
K-1 and M+3 are NOT consecutive odd numbers so this cannot be the true case.

(b) <------- M ---- (K-1) ---- K ---- (M+3) -------->
K-1 and M+3 are consecutive odds, so this must be the true case

Statement 2 is [spoiler]SUFFICIENT![/spoiler]

Therefore the answer is D.

Hope this helps!
:)
Whit
Whitney Garner
GMAT/GRE/EA Instructor & Anxiety/Accommodations Coach
www.whitneygarner.com

Contributor to Beat The GMAT!

Math is a lot like love - a simple idea that can easily get complicated :heart-eyes: