Twice a certain number minus 7 is equal to 5. What is the number.
2 answers:
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Answer:
The minimum average cost is $643.75
It should be built 62.5 machines to achieve the minimum average cost
Step-by-step explanation:
The equation that represents the cost C to produce x DVD/BLU-ray players is C = 0.04x² - 5x + 800
To find the minimum cost differentiate C to equate it by 0 to find the average cost per machine and to find the value of the minimum cost
∵ C = 0.04x² - 5x + 800
- Differentiate C with respect to x
∴
∴
- Equate by 0
∴ 0.08x - 5 = 0
- Add 5 to both sides
∴ 0.08x = 5
- Divide both sides by 0.08
∴ x = 62.5
That means the minimum average cost is at x = 62.5
Substitute the value of x in C to find the minimum average cost
∵ C = 0.04(62.5)² - 5(62.5) + 800
∴ C = 643.75
∵ C is the average cost
∴ The minimum average cost is $643.75
∵ x is the number of the machines
∴ It should be built 62.5 machines to achieve the minimum
average cost
Given:
Carrie has 180 ft of the fencing and wishes the fence to be 4times as long as it is wide.
To Find:
The area in square feet that the fencing encloses.
Answer:
The fence encloses 3600 sq ft.
Step-by-step explanation:
Let x denote the length of the dog run and y denote the width of the dog run.
Given that the garage wall serves as one side of the dog run, we are left with 3 other sides to instal the fence.
Carrie has 180ft of fencing with her, so the sum of the lengths of the 3 sides has to be equal to 180. We can represent this in the form of an equation as
We are also given that Carrie wishes the fence to be 4 times as long as it is wide.
So,
Replacing this value into the first equation, we have
Therefore,
Thus, the length of the dog run is 120ft and the width is 30ft.
The area enclosed will be equal to the length multiplied with the width. So,
The fence encloses 3600 sq ft.