Data Sufficiency

BTGmoderatorDC wrote:If n is an integer, is n + 1 odd?

(1) n + 2 is an even integer.
(2) n -1 is an odd integer.

OA D

Source: Official Guide

Target question: Is n + 1 odd?

Some important rules:
#1. ODD +/- ODD = EVEN
#2. ODD +/- EVEN = ODD
#3. EVEN +/- EVEN = EVEN


Statement 1: n + 2 is an even integer.
In other words: n + EVEN = EVEN
In other words: n = EVEN - EVEN
By Rule #3, n must be even, which means n+1 is ODD
The answer to the target question is YES, n+1 IS odd
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: n -1 is an odd integer.
In other words: n - ODD = ODD
In other words: n = ODD + ODD
By Rule #1, n must be even, which means n+1 is ODD
The answer to the target question is YES, n+1 IS odd
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer: D

Cheers,