1. A tank holds 1000 gallons of water, which drains from the bottom of the tank in half an hour. The values in the table show
the volume V of water remaining in the tank (in gallons) after
1 minutes.
5
10
15
20
25
30
1 (min)
V (gal)
694
444
250
111
28
0
(a) If P is the point (15, 250) on the graph of V, find the slopes
of the secant lines PQ when Q is the point on the graph
with 1 = 5, 10, 20, 25, and 30.
(b) Estimate the slope of the tangent line at P by averaging the
slopes of two secant lines.
(c) Use a graph of the function to estimate the slope of the
tangent line at P. (This slope represents the rate at which the
water is flowing from the tank after 15 minutes.)