SOLUTION: Kam traveled 240 miles east of St. Louis. For most of the trip he averaged 70mph, but for one period of time he slowed to 20 mph due to heavy traffic. If the total time of travel w

Algebra ->  Customizable Word Problem Solvers  -> Travel -> SOLUTION: Kam traveled 240 miles east of St. Louis. For most of the trip he averaged 70mph, but for one period of time he slowed to 20 mph due to heavy traffic. If the total time of travel w      Log On

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Question 469609: Kam traveled 240 miles east of St. Louis. For most of the trip he averaged 70mph, but for one period of time he slowed to 20 mph due to heavy traffic. If the total time of travel was 7 hours, how many miles did he travel at the reduced speed?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
Kam traveled 240 miles east of St. Louis. For most of the trip he averaged 70mph,
but for one period of time he slowed to 20 mph due to heavy traffic.
If the total time of travel was 7 hours, how many miles did he travel at the reduced speed?
:
Let r = total miles at reduced speed
then
(240-r) = total miles at 70 mph
:
Write a time equation, time = dist/speed
:
Fast time + slow time = 7 hrs
%28240-r%29%2F70 + r%2F20 = 7
Multiply by 140 to clear the denominators, results:
2(240-r) + 7r = 140(7)
480 - 2r + 7r = 980
-2r + 7r = 980 - 480
5r = 500
r = 500%2F5
r = 100 mi at 20 mph
:
:
See if that adds up, find the times:
(240-100)/70 = 2 hrs
100/20 = 5 hrs
------------------
total time = 7 hrs