Solutions
Get detailed explanations to advanced GMAT questions.
Question
If a, b, x and y are positive integers, is a^(-x) > b^(-y) ?
I. a < b
II. x < y
Option A:
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient to answer the question asked.
Option B:
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient to answer the question asked.
Option C:
BOTH statements (1) and (2) TOGETHER are sufficient to answer the question asked, but NEITHER statement ALONE is sufficient to answer the question asked.
Option D:
EACH statement ALONE is sufficient to answer the question asked.
Option E:
Statements (1) and (2) TOGETHER are NOT sufficient to answer the question asked, and additional data specific to the problem are needed.
Difficulty Level
EasySolution
Option C is the correct answer.
Option Analysis
We need to find a definite YES or NO.
Statement I is insufficient: a < b If a=2 and b = 8 and x = 1 and y = 1 then YES. But if a = 2 and b = 8 and x = 100 and y = 1 then NO. Insufficient.
Statement II is insufficient: x < y If a = 2 and b = 8 and x = 1 and y = 2 then YES. But if a = 100 and b = 1 then NO. Insufficient.
Together I and II, a < b and x < y,
We know that b>a and y>x. Thus:
1.b^y>a^y
2.a^y>a^x
Thus, b^y>a^x. Sufficient.
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