We know that
• The distance walked is 2.5 miles.
,
• She left at 4:00 pm and got home at 4:45 pm. She took 45 minutes to get there.
We can interpret the information as two points, the first one is (0,0) that represents the starting point. The second point is (45, 2.5), which represents the ending point when she arrived home. Let's graph these points and draw a line through them.
To find the slope, divide 2.5 miles by 45 minutes, that way we'll get the constant rate of change, which is the slope.
Therefore, the slope is 1/18 mi/min, which means Sonia walks at a rate of 1 mile every 18 minutes.