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?

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

To find the time Mary drove at 65 miles per hour, we first need to determine the time she drove at 55 miles per hour. Let's call this time "t1" in hours.

To find "t1," we can use the formula:

Distance = Speed x Time

Mary drove at 55 miles per hour for a certain amount of time. We know the distance she covered at this speed is not given, so we'll call it "d1." The equation becomes:

d1 = 55t1

Next, we can calculate the distance she covered at 65 miles per hour. Let's call this distance "d2," and the time she drove at this speed "t2" in hours. The equation becomes:

d2 = 65t2

We also know the total distance Mary drove is 555 miles. So, we have the equation:

d1 + d2 = 555

Now, let's substitute the earlier equations into the total distance equation:

55t1 + 65t2 = 555

Since Mary's total trip time was 9 hours, we can express it as:

t1 + t2 = 9

We can now solve this system of equations to find the values of t1 and t2.

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

455f52

To find the time Mary drove at 65 miles per hour, we first need to determine the time she drove at 55 miles per hour. Let's call this time "t1" in hours.