t = $√{(\;{pq}/{r} - r^2q)}$
Take the square of both sides
t$^2$ = $\;{pq}/{r}$ - r$^2$q
t$^2$ = $\;{pq - r^3q}/{r}$
cross multiply
rt$^2$ = pq - r$^3$q = q(p - r$^3$)
q = $\;{rt^2}/{p - r^3}$
