SOLUTION: Maria drove from Chicago, Illinois, to Milwaukee, Wisconsin, a distance of 90 miles, at a mean speed of 65 miles per hour. On her return trip, the traffic was much heavier, and her

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Question 357468: Maria drove from Chicago, Illinois, to Milwaukee, Wisconsin, a distance of 90 miles, at a mean speed of 65 miles per hour. On her return trip, the traffic was much heavier, and her mean speed was 42 miles per hour. Find Maria's mean speed for the round trip.
HINT: Divide the total distance by the total time. (Round the answer to one decimal place.)

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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Maria drove from Chicago, Illinois, to Milwaukee, Wisconsin, a distance of 90 miles, at a mean speed of 65 miles per hour. On her return trip, the traffic was much heavier, and her mean speed was 42 miles per hour. Find Maria's mean speed for the round trip.
:
Let s = average speed for the round trip
:
Write a time equation; time = dist/speed
:
to time + return time = total time
90%2F65 + 90%2F42 = 180%2Fs
1.3846 + 2.1429 = 180%2Fs
3.5275 = 180%2Fs
s = 180%2F3.5275
s = 51.0 mph average speed for the round trip