<PRE><B>Question 309272</B>
You drive 220 miles to see a friend.
 The return trip takes 20 minutes less than the original trip, and your average speed is 5 miles per hour faster. 
What is your average speed on the return trip?
:
Let s = return trip speed
then
(s-5) = original trip speed
:
Change 20 min to 1/3 hr
:
Write a time equation, Time = dist/speed
Original trip time - return trip time = 1/3 hr
{{{220/(s-5)}}} - {{{220/s}}} = {{{1/3}}}
multiply equation by 3s(s-5) results:
3s(220) - 3(s-5)*220 = s(s-5)
660s - 660(s - 5) = s^2 - 5s
660s - 660s + 3300 = s^2 - 5s
0 = s^2 - 5s - 3300
Factors to
(s-60)(s+55) = 0
s = +60 mph</PRE>