posted by Reid on .
Lee & Lynn started out on a trip at 8:00am and arrived at 4:00 pm. The next day they started back home at 11:00am using the same exact route. If their driving speed was constant for the entire trip, at what time would they have been at the same place at the same time on both days.
at time t on the first day, they were at distance (t-8)/8 of the way there.
at time t on the way back, they were (t-11)/8 of the way back, or 1-(t-11)/8 of the way out.
(t-8)/8 = 1 - (t-11)/8
t = 27/2 = 13:30
so, at 13:30 on the way out, they were 5 1/2 hours into the trip, with 2 1/2 hours to go.
on the way back, they were 2 1/2 hours into the trip, with 5 1/2 hours to go, so they were at the same place.