BTGmoderatorDC wrote:If each of the two digits X and Y is distinct, is the two digit integer XY prime?
(1) Each of the digits X and Y is the sum of 2 distinct single digit prime numbers.
(2) The sum of digits X and Y is 16.
Target question: Is the two-digit integer xy prime?
Given: Each of the two digits x and y is distinct
Statement 1: Each of the digits x and y is the sum of 2 distinct single digit prime numbers.
Let's TEST some values.
There are several values of x and y that satisfy statement 1. Here are two:
Case a: x = 3 + 5 = 8 and y = 2 + 7 = 9. So, xy = 89. In this case, the answer to the target question is
YES, xy IS prime
Case b: x = 2 + 7 = 9 and y = 3 + 5 = 8. So, xy = 98. In this case, the answer to the target question is
NO, xy is NOT prime
Since we cannot answer the
target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: The sum of digits x and y is 16
Since x and y are
DISTINCT DIGITS, there are only 2 possible ways to get a sum of 16. Let's examine each possible case:
Case a: x = 7 and y = 9. So, xy = 79. In this case, the answer to the target question is
YES, xy IS prime
Case b: x = 9 and y = 7. So, xy = 97. In this case, the answer to the target question is
YES, xy IS prime
Since each possible case yields the SAME answer to the target question, it MUST be the case that
xy IS prime
Since we can answer the
target question with certainty, statement 2 is SUFFICIENT
Answer: B
Cheers,
Brent
