value of xy

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j_shreyans Legendary Member Default Avatar
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value of xy

Post Thu Oct 16, 2014 8:31 pm
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  • Lap #[LAPCOUNT] ([LAPTIME])
    If x and y are positive integers , what is the value of xy?

    1) The greatest common factor of x and y is 10

    2) The least common multiple of x and y is 180

    OAC

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    Post Thu Oct 16, 2014 8:42 pm
    Target question: What is the value of xy?

    Statement 1: The greatest common factor of x and y is 10
    case a: x=10 and y=10. Here, xy=100
    case b: x=10 and y=20. Here, xy=200
    Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

    Statement 2: The least common multiple of x and y is 180
    case a: x=1 and y=180. Here, xy=180
    case b: x=2 and y=180. Here, xy=360
    Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

    Statements 1 & 2
    There's a nice rule that says:
    If x and y are positive integers, then (GCF of x and y)(LCM of x and y)=xy
    (aside: whenever a question mentions the LCM and the GCF, be sure to consider the above rule)
    Statement 1 says the GCF of x and y is 10
    Statement 2 says the LCM of x and y is 180
    So, from our handy rule, xy = (10)(180) = 1800
    Since we can now answer the target question with certainty, the combined statements are SUFFICIENT

    So, the answer is C

    Cheers,
    Brent

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