heyholetsgo
Is the integer n odd?
(1) n² - 2n is not a multiple of 4
(2) n is a multiple of 3
Target question: Is the integer n odd? Given: n is an INTEGER Statement 1: n² - 2n is not a multiple of 4. Factor to get:
n(n - 2) is NOT a multiple of 4
Underlying concepts:
Integer n is 2 greater than n-2
If n is ODD, then n-2 is also ODD, so n(n - 2) = (ODD)(ODD) = ODD. In this case, n(n-2) cannot be divisible by 4
If n is EVEN, then n-2 is also EVEN, so n(n - 2) = (EVEN)(EVEN) = EVEN. More importantly, n and n-2 are CONSECUTIVE even integers, and the product of two CONSECUTIVE even integers is always a multiple of 4Statement 1 tells us that
n(n - 2) is NOT a multiple of 4
So, it cannot be the case that n is EVEN
In other words,
it MUST be the case that n is ODDSince we can answer the
target question with certainty, statement 1 is SUFFICIENT
Statement 2: n is a multiple of 3There are several values of n that satisfy this condition. Here are two:
Case a: n = 3, in which case n
n is ODDCase b: n = 6, in which case n
n is EVENSince we cannot answer the
target question with certainty, statement 2 is NOT SUFFICIENT
Answer: A
Cheers,
Brent