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Math Help - Quantitative reasoning

  1. #1
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    Quantitative reasoning

    Hello,

    another quantitative reasoning question from my GRE booklet that I desperately need help with :

    The quantities of S and T are positive and related by the equation S= k/T where k is a constant. If the value of S increases by 50%, then the value of T decreases by what percent?

    a) 25%
    b) 33 1/3 %
    c) 50%
    d) 66 2/3 %
    e) 75%

    Any suggestions appreciated !
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  2. #2
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    Re: Quantitative reasoning

    pick some easy values to work with ...

    let S = 2

    k = 6

    T = 3

    T = k/S

    3 = 6/2

    increase S by 50% ...

    T = 6/3

    T = 2

    T changes from 3 to 2 ... a 33 1/3 % decrease
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  3. #3
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    Re: Quantitative reasoning

    Quote Originally Posted by fsiwaju View Post
    Hello,
    The quantities of S and T are positive and related by the equation S= k/T where k is a constant. If the value of S increases by 50%, then the value of T decreases by what percent?

    a) 25%
    b) 33 1/3 %
    c) 50%
    d) 66 2/3 %
    e) 75%
    If S and T are positive and S=\frac{k}{T} , then k must be a positive constant.
    So, let's assign positive numerical values to S, T, and k such that S=\frac{k}{T}.
    For example, let S=10, k=1000 and T=100.

    These values work for S=\frac{k}{T}.

    Then,
    1.5S=\frac{k}{T_*} \implies 1.5\left(10\right)=\frac{1000}{T_*} \implies T_* = \frac{1000}{15} = 66.\overline{66}

    T=100 and T_*=66.\overline{66}, which is a decrease of 33.\overline{33}\%.
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