Bunuel
If n is a positive integer, does n have four or more distinct factors?
(1) n is not prime
(2) 900 ≤ n < 1100
Given: n is a positive integer Target question: Does n have four or more distinct factors?Key property: If p is a prime number, then p² will have exactly 3 distinct factors: 1, p and p²
For example, 5 is prime. 5² = 25, and 25 has exactly three distinct factors: 1, 5 and 25
NOTE: In general, if p is prime, and n is a positive integer, then p^n will have exactly n+1 distinct factors.Given this, we can head straight to....
Statements 1 and 2 combined Statement 1 tells us that n is not prime
Statement 2 tells us that 900 ≤ n < 1100
There are several values of n that satisfy BOTH statements. Here are two:
Case a: If n = 1000 then the answer to the target question is
YES, n has four or more distinct factorsCase b: If n = 31² (note that 31 is prime AND 900 ≤ 31² < 1100) then n has exactly 3 distinct factors (1, 31 and 31²). So, the answer to the target question is
NO, n does not have four or more distinct factorsSince we can’t answer the
target question with certainty, the combined statements are NOT SUFFICIENT
Answer: E