<PRE><B>Question 195004</B>
A man made a 70-mile trip at a certain average rate.
 By increasing his average rate by 5 miles per hour, he traveled 80 miles in 
the same time that he spent on the 70-mile trip. Find his average rate on each trip. 
:
Let s = the original speed (70 mi trip)
then
(s+5) = the speed required for the 80 mi trip
:
The two trips have equal time; write a time equation; Time = {{{dist/speed}}}
:
80 mi time = 70 mi time
{{{80/((s+5))}}} = {{{70/s}}}
Cross multiply and you have:
80s = 70(s+5)
:
80s = 70s + 350
:
80s - 70s = 350
:
10s = 350
s = {{{350/10}}}
s = 35 mph original speed
then
35 + 5 = 40 mph is the faster speed
;
:
Check solution by finding the time of each trip
70/35 = 2 hr
80/40 = 2 hr</PRE>