SOLUTION: Traveling at an average speed of 60 miles per hour can give better gas mileage than traveling at higher speeds. Suppose you drive from one town to another and want to average 60 mi

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Question 505916: Traveling at an average speed of 60 miles per hour can give better gas mileage than traveling at higher speeds. Suppose you drive from one town to another and want to average 60 miles per hour for the trip. Road construction on the way there reduces your average speed to 30 miles per hour. If you drive 90 miles per hour on the return trip, what is your average speed for the entire trip?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
Suppose you drive from one town to another and want to average 60 miles per hour for the trip.
Road construction on the way there reduces your average speed to 30 miles per hour.
If you drive 90 miles per hour on the return trip, what is your average speed for the entire trip?
:
Well, you can't average 60 mph on this trip, when you get where you are going, you have already used up the time allotted for the whole trip
:
If you drive 90 on the return trip:
:
Let a = average for the whole trip
Let d = the one-way distance
:
Write a time equation, time = dist/speed
:
go time + return time = total time
d%2F30 + d%2F90 = %282d%29%2Fa
multiply by 90a, results
3da + da = 90(2d)
4da = 180d
divide by d
4a = 180
a = 180%2F4
a = 45 mph average for the round trip