college algebra

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A steel drum in the shape of a right circular cylinder is required to have a volume of 100 cubic feet. express the amount of material required to make the drum as a function of the radius r of the cylinder. also how much material is required if the drum is of radius 3 feet?

  • college algebra -

    V = pi r^2 h
    h = V/pi*r^2 = 100/(pi*r^2)
    A = 2pi*rh + 2pir^2
    A = 2*pi*r*100/(pi*r^2) + 2pi*r^2
    = 200/r + 2pi*r^2

    A(3) = 200/3 + 2pi*9 = 123.2 ft^2

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