Answer:
G descends about 8 ft per second
Explanation:
You want to know the descent rate of an airplane whose altitude is shown on a graph as being 1500 ft at 0 seconds and 0 ft at 180 seconds.
Rate of change
The airplane descended 1500 feet over a period of 180 seconds. That rate of change is ...
(-1500 ft)/(180 s) ≈ -8.333 ft/s
The plane descends about 8 feet per second.
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Additional comment
The slope of the line segment is the change in y divided by the change in x. For computing these changes, it is useful to consider points whose coordinates are obvious. Here, the y-intercept (1500 ft) and the x-intercept (180 seconds) are good choices.
The change in y from 1500 to 0 is a change of -1500. The change in x from 0 to 180 is a change of +180. The ratio of these changes is the slope, which is often designated by the letter m:
m = -1500/+180 = -25/3 = -8 1/3 . . . . . . about -8
The units of the slope are the ratio of the y-axis units to the x-axis units: feet/second.
The slope of -8 feet/second tells you the plane is descending about 8 feet per second.