Elaine drives her car 120

Question

miles and has an average of a certain speed. If the average speed had been 7mph
more, she could have traveled 141
miles in the same length of time. What was her average speed?

Answer 1

Let's call Elaine's average speed x mph.

According to the problem, she drives 120 miles at this speed. We can use the formula:

distance = rate x time

to find how long it took her:

120 miles = x mph * time

time = 120 miles / x mph

Now, if her average speed had been 7 mph more, we can set up another equation:

141 miles = (x + 7) mph * time

But we know that time is the same in both equations (since it's the amount of time it took Elaine to drive 120 miles), so we can substitute in our expression for time from the first equation:

141 miles = (x + 7) mph * (120 miles / x mph)

Simplifying this equation:

141 miles = (x + 7) * 120 miles / x

141x = 120x + 840

21x = 840

x = 40

So Elaine's average speed was 40 mph.