VJesus12 wrote:Eco Wildlife Preserve contains 5x zebras and 2x lions, where x is a positive integer. If the lions succeed in killing z of the zebras, is the new ratio of zebras to lions less than 2 to 1?
(1 ) z > x
(2 ) z = 4
Given: Eco Wildlife Preserve contains 5x zebras and 2x lions, where x is a positive integer. The lions kill z of the zebras
Target question: Is the new ratio of zebras to lions less than 2 to 1 ?
This is the perfect candidate for
rephrasing the target question.
ASIDE: If we take the time to rephrase the question in a simpler form, then we can save a ton of time evaluating the statements.
The NEW population of zebras is 5x - z
So, we can ask "
Is (5x - z)/2x < 2/1?"
Not bad, but
we can go much further than this!.
Since 2x is POSITIVE, we can safely take
(5x - z)/2x < 2/1 and multiply both sides by 2x.
When we do this, we get:
5x - z < 4x
Subtract 4x from both sides:
x - z < 0
Add z to both sides:
x < z
So, we can write....
REPHRASED target question: Is x < z?
Now onto the statements....
Statement 1: z > x
Perfect!!
The answer to the
REPHRASED target question is YES, x < z!
Since we can answer the
REPHRASED target question with certainty, statement 1 is SUFFICIENT
Statement 2: z = 4
Given this information, there is no way to conclude whether
x < z
Since we cannot answer the
REPHRASED target question with certainty, statement 2 is NOT SUFFICIENT
Aside: Here's a video with tips on rephrasing the target question: https://www.gmatprepnow.com/module/gmat- ... cy?id=1100
Answer: A
