blaster wrote:If x and y are positive integers and 3x + 5 < x + 11, is x a prime number?
(1) The sum of x and y is even.
(2) The product of x and y is odd.
how to solve this quesion? i don't see the relationship between x and y.
I think question is right.. My first thought was it might be wrong..
Let me explain:
3x + 5 < x + 11
-> x<3
The sum of x and y is even.
x,y are positive integers.
So x=1 or 2
what will be the value of y?
Sum of even number and even number is even.
Sum of two odd numbers is even
y can be either even or odd. When it is odd, x has to be 1 [to make the sum even]
when it is even, y has to be 2 [to make the sum even]
So x can be1 (non-prime) or 2(Prime).. INSUFFICIENT
The product of x and y is odd.
x=1 or 2
Product of two odd numbers is odd
X has to be odd, for the product xy to be odd.
hence x can be only 1 and not 2.
SUFFICIENT
pick B
