Walkabout
If x and y are integers, is x > y?
(1) x + y > 0
(2) y^x < 0
Given: x and y are integers Target question: If x and y are integers, is x > y? Statement 1: x + y > 0 This statement is clearly not sufficient.
There are many possible values of x and y that satisfy statement 1. Consider these two possible cases:
Case a: x = 2 and y = -1. In this case, the answer to the target question is
YES, x is greater than yCase b: x = -1 and y = 2. In this case, the answer to the target question is
NO, x is not greater than y Statement 2: y^x < 0If x and y are integers, and y^x < 0, then we can be certain of two things:
1) y is negative
2) x is odd
There are several values of x and y that satisfy these conditions. Here are two:
Case a: x = 3 and y = -1. In this case, the answer to the target question is
YES, x is greater than yCase b: x = -3 and y = -1. In this case, the answer to the target question is
NO, x is not greater than ySince we can’t answer the
target question with certainty, statement 2 is NOT SUFFICIENT
Statements 1 and 2 combined Statement 2 tells us that
y is negativeStatement 1 tells us that x + y > 0
If y is negative, and x + y > 0, then it must be the case that
x is positiveIf
x is positive and
y is negative, it must be the case that the answer to the target question is
YES, x is greater than ySince we can answer the
target question with certainty, the combined statements are SUFFICIENT
Answer: C
Cheers,
Brent