Answer
(a) 94.2 s
(b) $7.00\times10^{4}\,gal$
Work Step by Step
(a) $Diameter\,2r=0.500\,m/s\times30.0\,s=15.0\,m$
We need to find the time taken to travel a distance equal to the circumference of a circle with diameter 15.0 m
Circumference=$2\pi r=15.0\,m\times3.14=47.1\,m$
Time taken= $\frac{distance}{speed}=\frac{47.1\,m}{0.500\,m/s}=94.2\,s$
(b) $V=\pi r^{2}h$
In gallons, Volume $V=3.14\times(\frac{15.0\,m}{2})^{2}\times1.50\,m\times\frac{264.172\,gal}{1\,m^{3}}$
$=7.00\times10^{4}\,gal$