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If the operation @ is defined (OG16)

This topic has 1 expert reply and 0 member replies
boomgoesthegmat Senior | Next Rank: 100 Posts Default Avatar
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If the operation @ is defined (OG16)

Post Thu May 19, 2016 3:46 pm
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    If the operation @ is defined by x @ y = sqrt(xy) for all positive numbers x and y, then (5 @ 45) @ 60 =

    A) 30
    B) 60
    C) 90
    D) 30sqrt(15)
    E) 60sqrt(15)

    OA: A

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    Post Thu May 19, 2016 4:04 pm
    boomgoesthegmat wrote:
    If the operation @ is defined by x @ y = √(xy) for all positive numbers x and y, then (5 @ 45) @ 60 =

    A) 30
    B) 60
    C) 90
    D) 30√15
    E) 60√15

    OA: A
    I call these "Strange Operator" questions.
    We want to evaluate: (5 @ 45) @ 60

    Start with (5 @ 45)
    (5 @ 45) = √[(5)(45)]
    = √225
    = 15


    So, (5 @ 45) @ 60 = 15 @ 60
    From here, 15 @ 60 = √[(15)(60)]
    = √900
    = 30

    Answer: A

    RELATED RESOURCE (video)
    - Strange operators: https://www.gmatprepnow.com/module/gmat-algebra-and-equation-solving/video/976
    - Additional practice: https://www.gmatprepnow.com/module/gmat-algebra-and-equation-solving/video/977

    Cheers,
    Brent

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