SOLUTION: Ted walks from his home to the post office at an average rate of 3 miles per hour. he then runs back at an average rate of x miles per hour. Find x if his average for the entire tr

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Question 720545: Ted walks from his home to the post office at an average rate of 3 miles per hour. he then runs back at an average rate of x miles per hour. Find x if his average for the entire trip is 4.5 mph
Answer by josgarithmetic(39618) About Me  (Show Source):
You can put this solution on YOUR website!
________________speed_______________time________________distance
Walk To_________3___________________(___)_______________3
Run Back________x___________________(___)_______________3
Total___________(___)________________(___)_______________6

Try to fill the time information, because we may want distance divided by total time.

________________speed_______________time________________distance
Walk To_________3___________________(%283%2F3%29=1)_______________3
Run Back________x___________________(3%2Fx)_______________3
Total___________(___)________________(1%2B3%2Fx)_______________6

The total time is represented as 1%2B3%2Fx. Note that so far, all units are miles, hours, miles per hour.

We were given average speed for round trip was 4.5 miles per hour, so set this as 6%2F%281%2B3%2Fx%29=4.5 and solve for x.
Steps continuing could be,
6%2F%28%28x%2B3%29%2Fx%29=4.5
6x%2F%28x%2B3%29=4.5
6x=4.5%28x%2B3%29
.
and continue as best you know...