<PRE><B>Question 267516</B>
How far can a man drive out into the country at an average rate of 30 mph and return over the SAME road at the average of 50 mph, if he travels total time of 8 hours?
:
Let t = time driving at 50 mph
then
(8-t) = time driving at 30 mph
:
Write a distance equation, Dist = speed * time
:
Dist at 50 mph = dist at 30 mph
50t = 30(8-t)
50t = 240 - 30t
50t + 30t = 240
80t = 240
t = {{{240/80}}}
t = 3 hrs at 50 mph
then
8 - 3 = 5 hrs at 30 mph
:
Find the dist at 50 mph
3 * 50 = 150 mile
Check the dist at 30 mph, (should be the same)
5 * 30 = 150 miles
:
He can go 150 mi and satisfy the 8 hr requirement.</PRE>