Question 906491

Jane leaves her house
{{{d=60 mph*t}}}.....eq.1
the return trip, same distance
{{{d=70 mph*(t-15min)}}} .....eq.1....{{{15min=(15/60) h=0.25h}}}
{{{d=70 mph*(t-0.25h)}}}
since distance is same, we have
{{{60 mph*t=70 mph*(t-0.25h)}}} ....solve for t

{{{60 mph*t=70 mph*t-70mph*0.25h}}}

{{{60 (mil/h)*t-70( mil/h)*t=-70(mil/h)*0.25h}}}
{{{(60 (mil/h)-70 (mil/h))t=-17.5mil}}}

{{{-10(mil/h)t=-17.5mil}}}

{{{t=-17.5mil/-10 (mil/h)}}}
{{{t=1.75h}}}...............time when Jane leaves her house

{{{(t-0.25h)=(1.75h-0.25h)=1.50h}}}.. travel time back

total travel time in hours:
{{{1.75h+1.50h=3.25h}}} or 3 1/4 hours