Question 484014
: Michelle drove to a friend's house at a rate of 40mph.
 She returned by the same route at a rate of 45mph.
 The driving time for the round trip was 4 hours.
 What was the distance she traveled? 
:
let d = the one-way distance
then
2d = the total distance traveled
:
Write time equation: time = dist/speed
:
to time + return time = 4 hrs
{{{d/40}}} + {{{d/45}}} = 4
multiply by 360
360*{{{d/40}}} + 360*{{{d/45}}} = 4(360)
Cancel the denominators, results:
9d + 8d = 1440
17d = 1440
d = {{{1440/17}}}
d = 84.7
therefore
2 * 84.7 = 169.4 total distance traveled