Question 627413
d=rt
t=d/r

So, the boat that travels 9mph will travel .15 miles per minute.
{{{9/1*1/60=9/60=.15}}}
The boat that travels 10mph will travel .16 miles per minute.
{{{10/1*1/60=1/6=.16}}}

So, in order to get 57 minutes, we must take each boat's time from the origin and add those times.
{{{T(1)+T(2)=57}}}
{{{T=D/R}}}
{{{D(1)/R(1)+D(2)/R(2)=57}}}
R(1)=.15 miles per minute
R(2)=.16 miles per minute
{{{D(1)/.15+D(2)/.16=57}}}
{{{.16*D(1)+.15*D(2)=1.368}}}
{{{D(1)=.15*T}}}
{{{D(2)=.16*T}}}
{{{.16*.15*T+.15*.16*T=1.368}}}
{{{.048*T=1.368}}}
T=28.5 minutes
But we want hours, so .475 hours