Chapter 3.7, Problem 51E

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8th Edition

James Stewart

ISBN: 9781285740621

Textbook Problem

An oil refinery is located on the north bank of a straight river that is 2 km wide. A pipeline is to be constructed from the refinery to storage tanks located on the south bank of the river 6 km east of the refinery. The cost of laying pipe is $400,000/km over land to a point* P* on the north bank and $800,000/km under the river to the tanks. To minimize the cost of the pipeline, where should *P* be located?

To determine

**To minimize:**

To minimize the cost of the pipeline where should

Explanation

**1) Concept:**

Absolute minimum- let

**2) Given:**

Oil refinery is located on the north bank of a straight river that is

Pipeline length from refinery to storage banks is

The cost of laying pipe in millions of dollars is

The cost of laying pipes under the river, in millions of dollars is

**3) Formula:**

Differentiation formula-

**4) Calculation:**

Use the given information to draw a rough image

Let

Oil refinery is located on the north bank of a straight river that is

Pipeline length from refinery is

The cost of laying pipe in millions of dollars is

The cost of laying pipes under the river, in millions of dollars is

Therefore the cost of laying pipes on the land, in millions is

Therefore the cost of laying pipes under the river, in millions is

Therefore the total cost of laying pipes in millions of dollars, will be

To find the minimum cost, differentiate the cost function

Simplify

To find critical points, set

Add

Simplify

Multiply by

Simplify

Divide by

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P-46ESect-3.3 P-47ESect-3.3 P-48ESect-3.3 P-49ESect-3.3 P-50ESect-3.3 P-51ESect-3.3 P-52ESect-3.3 P-53ESect-3.3 P-54ESect-3.3 P-55ESect-3.3 P-56ESect-3.3 P-57ESect-3.3 P-58ESect-3.3 P-59ESect-3.3 P-60ESect-3.3 P-61ESect-3.3 P-62ESect-3.3 P-63ESect-3.3 P-64ESect-3.3 P-65ESect-3.3 P-66ESect-3.3 P-67ESect-3.3 P-68ESect-3.3 P-69ESect-3.3 P-70ESect-3.3 P-71ESect-3.3 P-72ESect-3.3 P-73ESect-3.3 P-74ESect-3.3 P-75ESect-3.3 P-76ESect-3.3 P-77ESect-3.4 P-1ESect-3.4 P-2ESect-3.4 P-3ESect-3.4 P-4ESect-3.4 P-5ESect-3.4 P-6ESect-3.4 P-7ESect-3.4 P-8ESect-3.4 P-9ESect-3.4 P-10ESect-3.4 P-11ESect-3.4 P-12ESect-3.4 P-13ESect-3.4 P-14ESect-3.4 P-15ESect-3.4 P-16ESect-3.4 P-17ESect-3.4 P-18ESect-3.4 P-19ESect-3.4 P-20ESect-3.4 P-21ESect-3.4 P-22ESect-3.4 P-23ESect-3.4 P-24ESect-3.4 P-25ESect-3.4 P-26ESect-3.4 P-27ESect-3.4 P-28ESect-3.4 P-29ESect-3.4 P-30ESect-3.4 P-31ESect-3.4 P-32ESect-3.4 P-33ESect-3.4 P-34ESect-3.4 P-35ESect-3.4 P-36ESect-3.4 P-37ESect-3.4 P-38ESect-3.4 P-39ESect-3.4 P-40ESect-3.4 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P-47ESect-3.9 P-48ESect-3.9 P-49ESect-3.9 P-50ESect-3.9 P-51ESect-3.9 P-52ESect-3.9 P-53ESect-3.9 P-54ESect-3.9 P-55ESect-3.9 P-56ESect-3.9 P-57ESect-3.9 P-58ESect-3.9 P-59ESect-3.9 P-60ESect-3.9 P-61ESect-3.9 P-62ESect-3.9 P-63ESect-3.9 P-64ESect-3.9 P-65ESect-3.9 P-66ESect-3.9 P-67ESect-3.9 P-68ESect-3.9 P-69ESect-3.9 P-70ESect-3.9 P-71ESect-3.9 P-72ESect-3.9 P-73ESect-3.R P-1CCSect-3.R P-2CCSect-3.R P-3CCSect-3.R P-4CCSect-3.R P-5CCSect-3.R P-6CCSect-3.R P-7CCSect-3.R P-8CCSect-3.R P-9CCSect-3.R P-10CCSect-3.R P-11CCSect-3.R P-1TFQSect-3.R P-2TFQSect-3.R P-3TFQSect-3.R P-4TFQSect-3.R P-5TFQSect-3.R P-6TFQSect-3.R P-7TFQSect-3.R P-8TFQSect-3.R P-9TFQSect-3.R P-10TFQSect-3.R P-11TFQSect-3.R P-12TFQSect-3.R P-13TFQSect-3.R P-14TFQSect-3.R P-15TFQSect-3.R P-16TFQSect-3.R P-17TFQSect-3.R P-18TFQSect-3.R P-19TFQSect-3.R P-1ESect-3.R P-2ESect-3.R P-3ESect-3.R P-4ESect-3.R P-5ESect-3.R P-6ESect-3.R P-7ESect-3.R P-8ESect-3.R P-9ESect-3.R P-10ESect-3.R P-11ESect-3.R P-12ESect-3.R P-13ESect-3.R P-14ESect-3.R P-15ESect-3.R P-16ESect-3.R P-17ESect-3.R P-18ESect-3.R P-19ESect-3.R P-20ESect-3.R P-21ESect-3.R P-22ESect-3.R P-23ESect-3.R P-24ESect-3.R P-25ESect-3.R P-26ESect-3.R P-27ESect-3.R P-28ESect-3.R P-29ESect-3.R P-30ESect-3.R P-31ESect-3.R P-32ESect-3.R P-33ESect-3.R P-34ESect-3.R P-35ESect-3.R P-36ESect-3.R P-37ESect-3.R P-38ESect-3.R P-39ESect-3.R P-40ESect-3.R P-41ESect-3.R P-42ESect-3.R P-43ESect-3.R P-44ESect-3.R P-45ESect-3.R P-46ESect-3.R P-47ESect-3.R P-48ESect-3.R P-49ESect-3.R P-50ESect-3.R P-51ESect-3.R P-52ESect-3.R P-53ESect-3.R P-54ESect-3.R P-55ESect-3.R P-56ESect-3.R P-57ESect-3.R P-58ESect-3.R P-59ESect-3.R P-60ESect-3.R P-61ESect-3.R P-62ESect-3.R P-63ESect-3.R P-64ESect-3.R P-65ESect-3.R P-66ESect-3.R P-67ESect-3.R P-68ESect-3.P P-1PSect-3.P P-2PSect-3.P P-3PSect-3.P P-4PSect-3.P P-5PSect-3.P P-6PSect-3.P P-7PSect-3.P P-8PSect-3.P P-9PSect-3.P P-10PSect-3.P P-11PSect-3.P P-12PSect-3.P P-13PSect-3.P P-14PSect-3.P P-15PSect-3.P P-16PSect-3.P P-17PSect-3.P P-18PSect-3.P P-19PSect-3.P P-20PSect-3.P P-21PSect-3.P P-22PSect-3.P P-23PSect-3.P P-24P

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