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Thread: Related Rates

  1. #1
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    Related Rates

    If the volume of a cube is increasing at $\displaystyle 24 in^3/min$ and the surface area of the cube is increasing at $\displaystyle 12in^2/min$
    , what is the length of each edge of the cube?
    A. 2
    B$\displaystyle 2 \sqrt{2}$
    C. $\displaystyle 12^{1/3}$
    D. 4
    E. 8

    Answers are in inches.

    This is what I know:
    Dv/dt= 24
    and DSA/dt= 12

    $\displaystyle v= s^3$
    SA= 3s...I think

    So,
    Dv/dt= 3s ds/dt
    dSA/dt= 2 ds/dt

    Ds/dt= $\displaystyle \frac{dv/dt}{3s}$

    Now what?

    Thanks!
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  2. #2
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    Surface Area of a Cube is $\displaystyle 6s^{2}$.
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