npar">
      <span class="bmw">See 3.10 for more
      practice.</span><span class="larsonfive">See Larson 3.7 and
      4.8.</span>
    </div>
      The volume of a right circular cylinder is $V(r,h)= \pi
    r^2 h$. Imagine that each of $V$, $r$, and $h$ depends on $t$
    (we might be collecting rain water in a can, or crushing a
    cylindrical concentrated juice can, etc.).

    <ol>
      <li>If the height remains constant, but the radius changes,
      what is $dV/dt$ in terms of $dr/dt$? Use this to