Select all the expressions that are equivalent to 4

A fence must be built to enclose a rectangular area of 20,000 ft^2. Fencing material costs $4 per foot for the two sides facing

Marysya12 [62]

The cost of the least expensive fence is $3200

Step-by-step explanation:

The given is:

A fence must be built to enclose a rectangular area of 20,000 ft²
Fencing material costs $4 per foot for the two sides facing north and south and $8 per foot for the other two sides

We need to find the cost of the least expensive fence

Assume that the length of each side opposite to North or South is x feet and the length of each other sides is y feet

∵ The length of the rectangle = x feet

∵ The width of the rectangle = y feet

∵ The rectangular area is 20,000 ft²

- Area of a rectangle = length × width

∴ x × y = 20,000

- Divide both sides by x to find y in terms of x

∴ $y=\frac{20,000}{x}$

The fence's length is equal to the perimeter of the rectangular area

∵ Perimeter of the rectangle = 2 length + 2 width

∴ Perimeter of the rectangle = 2x + 2y

∵ Fencing material costs $4 per foot for the two sides facing

North and South

∴ x costs $4 per foot

∵ The cost of the other two sides is $8 per foot

∴ y costs $8 per feet

The cost of the fence is the sum of the products of 4 , 2x and 8 , 2y

∵ The cost of the fence (C) = 4(2x) + 8(2y)

∴ C = 8x + 16y

- Substitute y by its value above

∴ $C=8x+16(\frac{20,000}{x})$

∴ $C=8x+\frac{320,000}{x}$

To find the least expensive differentiate C with respect to x and equate the answer by 0 to find the value of x

∵ $\frac{320,000}{x}$ can be written as $320,000x^{-1}$

∴ $C=8x+320,000x^{-1}$

∵ $\frac{dC}{dx}=8(1)x^{1-1}+320,000(-1)x^{-1-1}$

∴ $\frac{dC}{dx}=8-320,000x^{-2}$

- Equate $\frac{dC}{dx}$ by zero

∴ $8-320,000x^{-2}=0$

∵ $-320,000x^{-2}=-\frac{320,000}{x^{2}}$

∴ $8-\frac{320,000}{x^{2}}=0$

- Subtract 8 from both sides

∴ $-\frac{320,000}{x^{2}}=-8$

- Multiply both sides by x²

∴ - 320,000 = - 8x²

- Divide both sides by -8

∴ 40,000 = x²

- Take √ for both sides

∴ 200 = x

Substitute x in the equation of C to find the least cost of fence

∵ $C=8(200)+\frac{320,000}{(200)}$

∴ C = 1600 + 1600

∴ C = 3200

The cost of the least expensive fence is $3200

Learn more:

You can learn more about the differentiation in brainly.com/question/4279146

#LearnwithBrainly

5 0

2 years ago

Find the LCM of the numbers.<br> 3,16,20

KengaRu [80]

Answer:

240

Step-by-step explanation:

find multiples of 3 16 and 20 and multiply the multiples . you will get 240 .

i hop it helps you ❤

3 0

2 years ago

Find the complex conjugate of z1 of z1=8+i

kakasveta [241]

Answer:

this is just math jargon... a conjugate is the same numbers but with an opposite sign.. got it?

Step-by-step explanation:

z1' ( the prime is often used for conjuates it's also used in calculus but later)

Z1' =8-i

8 0

3 years ago

The ball used in a soccer game may not weigh more than 16 ounces or less

Liono4ka [1.6K]

In order for the ball to be used in the game, it must be able to meet the minimum and maximum weight requirements. These are the limits of the weight of the ball. If it exceeds the maximum limit of 16 ounces or below the minimum limit of 14 ounces, the ball will not be approved.

So, by adding 1.5 ounces, that would mean that the initial weight of the ball did not reach the minimum limit. The initial weight of the ball, denoted as x, have two possible values. The first value is the initial weight plus added with 1.5 ounces would reach 14 ounces.

x + 1.5 = 14
x = 12.5 ounces

The other scenario is when the initial weight is added to reach the maximum requirement of 16 ounces

x + 1.5 = 16
x = 14.5 ounces

From both answer, we could conclude that the initial weight has to be 12.5 ounces. If the initial weight were 14.5 ounces to begin with, there should be no need for air. It cans till be approved to be used.

3 0

3 years ago

Ahat costs $25. Tax is 8%. How much is the lax on the hot? O $20 $17 $0 20 $2 NEXT QUESTION ASK TORTILLP

LuckyWell [14K]

Answer:

$2

Step-by-step explanation:

To use a percent you must change it to a decimal.

8% is .08

To find 8% of 25, we use multiplication.

.08 × 25

= 2

In case you cannot use a calculator or you want to be very quick about this, or just do a simple check... you can actually reverse the number (money, amount, etc) and the percent.

25% of 8 is not bad for doing mental math. 25% is a quarter, or 1/4 of 8 which again is 2.

5 0

2 years ago

Select all the expressions that are equivalent to 4 - x.