Question

A coordinate plane shows the x-axis, labeled as hours, ranging from 0 to 6 in increments of 1 and the y-axis, labeled as gallons, ranging from 0 to 240 in increments of 20. A line segment joins four plotted points. The coordinates of the plotted points are (0, 200), (1, 160), (3, 80), and (5, 0).
The graph shows the number of gallons in a wading pool that is being drained. Using the points (1,160) and (3,80) as (x1, y1) and (x2, y2), what is the rate of change in the number of gallons in the pool after each hour has passed?
A. -40 gal./hr.
B. -1/40 gal./hr.
C. 1/40 gal./hr.
D. 40 gal./hr.

Answer 1

Slope = (80 - 160) / (3 - 1) = -80 / 2 = -40, so the pool loses 40 gallons per hour. Answer: A. -40 gal./hr.