Answer
The expression for sphere volume is incorrect in Exercise 12.
Volume of a sphere in terms of diameter $d$ is $V=\pi d^3/6$.
Work Step by Step
The correct equation for sphere volume is given as, $V=\frac{4}{3}\pi r^3$.
diameter is expressed as $d=2r$. Substituting, for $r$ in equation for volume -
$V=\frac{4}{3}\pi (\frac{d}{2})^3=\frac{4}{3}\pi \frac{d^3}{8} = \frac{1}{6}\pi d^3$.
The expression for sphere volume in Exercise 12 is incorrect.
