BTGModeratorVI wrote: ↑Thu Jul 23, 2020 6:37 am
If x, y, and z are distinct positive integers, is x(y – z) less than y(x – z) ?
(1) y > x
(2) x > z
Answer:
A
Source: Kaplan
Target question: Is x(y – z) < y(x – z) ?
This is a great candidate for REPHRASING the target question.
Target question:
Is x(y – z) < y(x – z) ?
Expand both sides of inequality: xy - xz < xy - yz
Subtract xy from both sides: -xz < -yz
Add yz to both sides to get: yz - xz < 0
Factor the left side: z(y - x) < 0
Since we know z is POSITIVE, let's divide both sides by z to get:
y - x < 0
.....
REPHRASED target question: Is y - x < 0 ?
Statement 1: y > x
Subtract x from both sides to get:
y - x > 0
PERFECT!!
Since we can answer the
REPHRASED target question with certainty, statement 1 is SUFFICIENT
Statement 2: x > z
This does not help us answer the
REPHRASED target question because they're no information about y
Since we cannot answer the
target question with certainty, statement 2 is NOT SUFFICIENT
Answer: A
