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 t minutes. (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 t=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 V 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.)
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Textbook Solutions for Calculus: Early Transcendentals
Question
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 t minutes.
\(\begin{array}{|c|c|c|c|c|c|c|}
\hline t(\min ) & 5 & 10 & 15 & 20 & 25 & 30 \\
\hline V(\mathrm{gal}) & 694 & 444 & 250 & 111 & 28 & 0 \\
\hline
\end{array}\)
(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 t = 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 V 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.)
Solution
Step 1 of 4
(a)
The slope equation for the given values is given by,
\(\begin{aligned}
m & =\frac{P_{v}-Q_{V}}{P_{t}-Q_{t}} \\
& =\frac{250-Q_{v}}{15-Q_{t}}
\end{aligned}\)
For t = 5,
\(\begin{aligned}
m & =\frac{250-694}{15-5} \\
& =-44.4
\end{aligned}\)
For t = 10,
\(\begin{aligned}
m & =\frac{250-444}{15-10} \\
& =-38.8
\end{aligned}\)
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