Question

On a 9-hour trip home from winter break, Mary was forced to drive on a stretch of highway that had a lot of construction. At first she had to go 55 miles per hour for a certain amount of time, but then she was able to go 65 miles per hour for the rest of the trip and in total she drove 555 miles. Assuming she made no stops, how long did she drive 65 miles per hour?

Answer 1

since distance = speed * time, just add up the distances:

55(9-x)+65x = 555
x = 6

Answer 2

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