At a supermarket, a 6-ounce bottle of

A cylinder shaped can needs to be constructed to hold 500 cubic centimeters of soup. The material for the sides of the can costs

iogann1982 [59]

Answer:

r=3.628cm

h=12.093cm

Step-by-step explanation:

For this problem we are going to use principles, concepts and calculations from multivariable calculus; mainly we are going to use the Lagrange multipliers method. This method is thought to help us to find a extreme value of a multivariable function 'F' given a restriction 'G'. F represents the function that we want to optimize and G is just a relation between the variables of which F depends. The Lagrange method for just one restriction is:

$\nabla F=\lambda \nabla G$

First, let's build the function that we want to optimize, that is the cost. The cost is a function that must sum the cost of the sides material and the cost of the top and bottom material. The cost of the sides material is the unitary cost (0.03) multiplied by the sides area, which is $A_s=2\pi rh$ for a cylinder; while the cost of the top and bottom material is the unitary cost (0.05) multiplied by the area of this faces, which is $A_{TyB}=2\pi r^2$ for a cylinder.

So, the cost function 'C' is:

$C=2\pi rh*0.03+2\pi r^2*0.05\\C=0.06\pi rh+0.1\pi r^2$

The restriction is the volume, which has to be of 500 cubic centimeters:

$V=500=\pi r^2h\\500=\pi hr^2$

So, let's apply the Lagrange multiplier method:

$\nabla C=\lambda \nabla V\\\frac{\partial C}{\partial r}=0.06\pi h+0.2\pi r\\\frac{\partial C}{\partial h}=0.06\pi r\\\frac{\partial V}{\partial r}=2\pi rh\\\frac{\partial V}{\partial h}=\pi r^2\\(0.06\pi h+0.2\pi r,0.06\pi r)=\lambda (2\pi rh,\pi r^2)$

At this point we have a three variable (h,r, λ)-three equation system, which solution will be the optimum point for the cost (the minimum). Let's write the system:

$0.06\pi h+0.2\pi r=2\lambda \pi rh\\0.06\pi r=\lambda \pi r^2\\500=\pi hr^2$

(In this kind of problems always the additional equation is the restricion, in this case, V=500).

Let's divide the first and second equations by π:

$0.06h+0.2r=2\lambda rh\\0.06r=\lambda r^2\\500=\pi hr^2$

Isolate λ from the second equation:

$\lambda =\frac{0.06}{r}$

Isolate h from the third equation:

$h=\frac{500}{\pi r^2}$

And then, replace λ and h in the first equation:

$0.06*\frac{500}{\pi r^2} +0.2r=2*(\frac{0.06}{r})r\frac{500}{\pi r^2} \\\frac{30}{\pi r^2}+0.2r= \frac{60}{\pi r^2}$

Multiply all the resultant equation by $\pi r^{2}$ :

$30+0.2\pi r^3=60\\0.2\pi r^3=30\\r^3=\frac{30}{0.2\pi } =\frac{150}{\pi}\\r=\sqrt[3]{\frac{150}{\pi}}\approx 3.628cm$

Then, find h by the equation $h=\frac{500}{\pi r^2}$ founded above:

$h=\frac{500}{\pi r^2}\\h=\frac{500}{\pi (3.628)^2}=12.093cm$

4 0

3 years ago

The mean of six numbers is 8, and the mean of another four numbers is 5.

Ket [755]

Answer:

6.8

Step-by-step explanation:

8 * 6 = 48 (to reverse dividing by 6 to basically un-average the 6 numbers).

5 * 4 = 20 (to un-average these numbers as well).

48 + 20 = 68

68 / 10 = 6.8

Basically by doing this you are still adding all the numbers together & then dividing by 10 as if you added them all up at once & not in a group of 6 & a group of 4.

Hope this helped. :)

4 0

3 years ago

Find a so that the point (-1,5) is on the graph of f(x)=ax2+1

sasho [114]

Step-by-step explanation:

to solve for a,

f(-1) = 5

a(-1)^2 + 1 = 5

a + 1 = 5, so a=4

7 0

3 years ago

The composition Rx T -2.4 is performed on BC. What are the coordinates of B'' and C''?

const2013 [10]

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7 0

3 years ago

Read 2 more answers

The Baldwin family walked of a mile in of an hour. What is their unit rate in miles per hour? (5 points)

Lisa [10]

So walked 4/5 mile in a 4/9 h so just use the rule of 3 simple

60 minutes ------ 1 hour
x min. ----------- 4/9 h
--------------------------------
x = 4/9 *60/1 = 240/9 = 26,6 min.

4/5 mile -------in 26,6 min.
1 mile -------- x min.
-----------------------------
x = 1*26,6/(4/5) = 26,6 /(0,8) = 33,25 min.

1 mile ..... 33,25 min.
x miles ----- 60 min.
---------------------------
x = 60/33,25 = 1,8 miles

so their unit rate in miles per hour will be 1,8 miles / hour

hope this will help you.

3 0

3 years ago