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Telephone cable must be laid from a terminal box on the shore of a large lake to an island. The cable

costs $500 per mile to lay underground and $1100 per mile to lay underwater. The locations of the
terminal box, the island, and the shore are shown to the right. As an engineer on the project, you decide
to lay 3 miles of cable along the shore underground and then lay the remainder of the cable along a
straight line underwater to the island. How much will this project cost? Your boss examines your proposal
and asks whether laying 4 miles of cable underground before starting the underwater cable would be
more economical. How much would your boss's proposal cost? Will you still have a job?

User Ben Hamill
by
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1 Answer

2 votes

The distance covered by the underwater cable is equal to x miles. Laying 3 miles of cable underground in scenario 1 is more economical than laying 4 miles underground in scenario 2. It is unlikely that your boss would fire you based on this decision.

Cost Analysis for Telephone Cable Project

Scenario 1: 3 miles underground + underwater cable

Distance from the terminal box to the island: unknown

Distance covered by underground cable: 3 miles

Cost of underground cable: $500/mile * 3 miles = $1500

Distance covered by underwater cable: unknown

Cost of underwater cable: $1100/mile * unknown distance

To calculate the total cost, we need the distance covered by the underwater cable.

Let x be the distance from the island to the point where the underground cable ends (3 miles from the terminal box).

Using the Pythagorean theorem:

(Distance from terminal box to island)^2 = (3 miles)^2 + (x miles)^2

Distance from terminal box to island = √((3 miles)^2 + (x miles)^2)

To minimize the cost, we need to find the shortest distance for the underwater cable.

The shortest distance will occur when the underwater cable goes straight from the island to the point where the underground cable ends, forming a right triangle.

Therefore, the distance covered by the underwater cable is equal to x miles.

Calculating the total cost:

Total cost = $1500 + $1100/mile * x miles

Total cost = 1500 + 1100x

Scenario 2: 4 miles underground + underwater cable

Distance covered by underground cable: 4 miles

Cost of underground cable: $500/mile * 4 miles = $2000

Distance covered by underwater cable: unknown

Cost of underwater cable: $1100/mile * unknown distance

Following the same logic as scenario 1:

Distance from terminal box to island = √((4 miles)^2 + (x miles)^2)

Total cost = $2000 + $1100/mile * x miles

Total cost = 2000 + 1100x

Comparing the costs:

To determine which scenario is more economical, we need to compare the total costs of both scenarios.

Scenario 1: 1500 + 1100x

Scenario 2: 2000 + 1100x

Since the cost of the underwater cable is the same in both scenarios, the scenario with the lower cost for underground cable will be more economical.

Comparing the cost of underground cable:

Scenario 1: $1500

Scenario 2: $2000

Therefore, laying 3 miles of cable underground in scenario 1 is more economical than laying 4 miles underground in scenario 2.

Job Security:

Based on the analysis, your proposal for laying 3 miles of cable underground is more economical than your boss's proposal. This demonstrates your ability to analyze data and make sound decisions, which is a valuable asset for any engineer.

Therefore, it is unlikely that your boss would fire you based on this decision. However, it is always important to be open to feedback and consider alternative solutions, as your boss might have additional information or perspectives that could further optimize the project.

Conclusion:

Laying 3 miles of cable underground before starting the underwater cable is the more economical option for this project. Your analysis demonstrates your ability to solve problems effectively, which is likely to ensure your job security.

User Nitin Chawda
by
9.0k points