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OG2015 DS If x and y

This topic has 1 expert reply and 0 member replies
lionsshare Senior | Next Rank: 100 Posts
Joined
09 Aug 2017
Posted:
62 messages

OG2015 DS If x and y

Post Sat Sep 16, 2017 10:21 pm
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    If x and y are positive, is x/y greater than 1 ?

    (1) xy > 1
    (2) x - y > 0

    OA: B

    Anyone, please what's the solution to the problem. Bunch of thanks!

    Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums!
    Post Sun Sep 17, 2017 5:31 am
    lionsshare wrote:
    If x and y are positive, is x/y greater than 1 ?

    (1) xy > 1
    (2) x - y > 0

    Target question: Is x/y > 1?

    Given: x and y are positive

    Statement 1: xy > 1
    This statement doesn't FEEL sufficient, so I'll TEST some values.
    There are several values of x and y that satisfy statement 1. Here are two:
    Case a: x = 1 and y = 2. Here, x/y = 1/2, which means x/y < 1
    Case b: x = 2 and y = 1. Here, x/y = 2/1 = 2, which means x/y > 1
    Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

    Aside: For more on this idea of plugging in values when a statement doesn't feel sufficient, you can read my article: http://www.gmatprepnow.com/articles/data-sufficiency-when-plug-values

    Statement 2: x-y > 1
    With this statement, it might be useful to consider rephrasing the target question.

    Aside: Here’s a video with tips on rephrasing the target question: http://www.gmatprepnow.com/module/gmat-data-sufficiency?id=1100

    Since x and y are positive, we can take the inequality x/y > 1 and multiply both sides by y to get: x > y.
    Now let's subtract both sides by y to get: x - y > 0

    So, let's REPHRASE the target question...
    REPHRASED target question: Is x-y > 0?

    Statement 2 tells us that x - y > 1
    Since 1 > 0, we can say that x - y > 1 > 0
    So, we can conclude that x - y > 0
    Since we can answer the REPHRASED target question with certainty, statement 2 is SUFFICIENT

    Answer = B

    Cheers,
    Brent

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