The average amount of water used per person can be determined by finding the slope of the line. The formula for determining slope is expressed as
Slope = (y2 - y1)/(x2 - x1)
The amount of water usage are the values of y and the number of people are the values of x. From the graph,
when x1 = 0, y1 = 0
when x2 = 8, y2 = 100
Slope = (100 - 0)/(8 - 0) = 100/8
slope = 12.5
Thus, the average amount of water used per person is 12.5 gallons
