AP Calc Questions-Related Rates

<p>I understood related rates until my teacher gave us these AP questions. Any help/suggestions would be appreciated:</p>

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<li><p>At time t, t>= 0, the volume of a sphere is increasing at a rate proportional to the reciprocal of its radius. At t = 0, the radius of the sphere is 1 and at t = 15, the radius is 2. A) Find the radius of the spehere as a function of t. B) At what time t will the volume of the sphere be 27 times its volume at t=0?</p></li>
<li><p>The volume of a cone (V=1/3 pi r^2h) is increasing at the rate of 28pi cubic units per second. At the instant when the raidius r of the cone is 3 units, the volume is 12pi cubic units and the radius is increasinf at 1/2 unit per second. A) At the instant when the radius of the cone is 3 units, what is the rate of change of the area of its base? B) At the instant when the radius of the cone is 3 units, what is the rate of change of its height h? C) At the instant when the radius of the cone is 3 units, what is the instaneous rate of change of the area of its base with respect to its height h?</p></li>
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