Bunuel
Is the positive integer n odd?
(1) n = 2k + 1, where k is a positive integer.
(2) 2n + 1 is an odd integer.
Target question: Is the positive integer n odd? Statement 1: n = 2k + 1, where k is a positive integerThis is the classic definition of an odd integer.
That is, ALL odd integers can be written in the form 2k + 1, where k is a positive integer
This should make sense because, if k is an integer, then 2k will be an EVEN integer, which means 2k+1 must be an ODD integer.
In other words,
n must be an odd integerSince we can answer the
target question with certainty, statement 1 is SUFFICIENT
Statement 2: 2n + 1 is an odd integer As mentioned above, 2n + 1 will be an odd integer for ALL values of n.
Consider these two cases:
Case a: If
n = 2, then 2n + 1 = 2(2) + 1 = 5, which is odd. In this case, the answer to the target question is
NO, n is not oddCase b: If
n = 3, then 2n + 1 = 2(3) + 1 = 7, which is odd. In this case, the answer to the target question is
YES, n is oddSince we can’t answer the
target question with certainty, statement 2 is NOT SUFFICIENT
Answer: A
Cheers,
Brent