VJesus12 wrote:If s is a positive integer, is s prime?
(1) 21/s is an integer
(2) 47/s is an integer
Target question: Is s prime?
Given: s is a positive integer
Statement 1: 21/s is an integer
So, s can equal 1, 3, 7 or 21
If s = 1, the answer to the target question is
NO, s is NOT prime
If s = 3, the answer to the target question is
YES, s IS prime
Since we cannot answer the
target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: 47/s is an integer
So, s can equal 1 or 47
If s = 1, the answer to the target question is
NO, s is NOT prime
If s = 47, the answer to the target question is
YES, s IS prime
Since we cannot answer the
target question with certainty, statement 2 is NOT SUFFICIENT
Statements 1 and 2 combined
Statement 1 tells us that s can equal 1, 3, 7 or 21
Statement 2 tells us that s can equal 1 or 47
Since BOTH statements must be true, it MUST be the case that s = 1
Since s = 1, the answer to the target question
must be NO, s is NOT prime
Since we can answer the
target question with certainty, the combined statements are SUFFICIENT
Answer: C
Cheers,
Brent
