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math (Caluclas)

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A spherical ballon is leaking air at 2 cubic inches per hour.l How fast is the ballons radisu chancing when the radisu si 3 inches.

  • math (Caluclas) -

    v = 4/3 pi r^3

    dv/dt = 4pi r^2 dr/dt

    -2 = 4pi*9 dr/dt

    dr/dt = -2/36pi = -1/18pi = -.0177 in/hr

  • Caluclas ? -

    What is a radisu?
    Once I can understand as a typo, but twice ?

    V= (4/3)πr^3
    dV/dt = 4π r^2 dr/dt
    -2 = 4π(9)dr/dt


  • math (Caluclas) -

    Sorry about that Reiny. I have a quick question though, where does the 9 come from?

  • math (Caluclas) -

    Notice both Steve and I have the same derivative equation of
    dV/dt = 4π r^2 dr/dt

    what is the value of r^2 when r = 3 ?

  • math (Caluclas) -

    Oh okay. I understand that, i was just not understand where the 9 came from, but i see now. Thank you both

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