Question 1060486
A spherical balloon is to be deflated so that its 
radius decreases at a constant rate of 11 cm/min. 
At what rate must air be removed when the radius 
is 9 cm.
<pre><b>
{{{V}}}{{{""=""}}}{{{expr(4/3)*pi*r^3}}}

{{{dV/dt}}}{{{""=""}}}{{{4*pi*r^2*expr(dr/dt)}}}

{{{dV/dt}}}{{{""=""}}}{{{4*pi*(matrix(1,2,9,cm))^2*(matrix(1,2,-11,cm/min))}}}

{{{matrix(1,4,dV/dt,"(at",that,"instant)")}}}{{{""=""}}}{{{matrix(1,2,-396pi,cm^3/min)}}}

The negative signs are because the radius and the volume 
are both decreasing.

Edwin</pre></b>