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3 years ago

7

If Yoko walks 1 block in 3 minutes, how long does it take her to walk from the school to the library? How long does it take her

to walk from home to school?

1 answer:

mojhsa [17]3 years ago

6 0

Answer:

from school to the library it would take 21 minutes, home to school would be 5

Step-by-step explanation:

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Three times a number minus 2 is 25. What is the number?

Verizon [17]

3×9=27-2=25
3× what # - 2= 25

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Annette [7]

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Cindy and Giovanni plan to make spaghetti sauce. Cindy needs 4 and three-fourths pounds of tomatoes for her recipe. Giovanni nee

Flauer [41]

(4 3/4) + (5 3/4) = (4 + 5) + (3/4 + 3/4)

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A metal cylinder can with an open top and closed bottom is to have volume 4 cubic feet. Approximate the dimensions that require

Aleksandr-060686 [28]

Answer:

$r\approx 1.084\ feet$

$h\approx 1.084\ feet$

$\displaystyle A=11.07\ ft^2$

Step-by-step explanation:

<u>Optimizing With Derivatives </u>

The procedure to optimize a function (find its maximum or minimum) consists in :

Produce a function which depends on only one variable
Compute the first derivative and set it equal to 0
Find the values for the variable, called critical points
Compute the second derivative
Evaluate the second derivative in the critical points. If it results positive, the critical point is a minimum, if it's negative, the critical point is a maximum

We know a cylinder has a volume of 4 $ft^3$ . The volume of a cylinder is given by

$\displaystyle V=\pi r^2h$

Equating it to 4

$\displaystyle \pi r^2h=4$

Let's solve for h

$\displaystyle h=\frac{4}{\pi r^2}$

A cylinder with an open-top has only one circle as the shape of the lid and has a lateral area computed as a rectangle of height h and base equal to the length of a circle. Thus, the total area of the material to make the cylinder is

$\displaystyle A=\pi r^2+2\pi rh$

Replacing the formula of h

$\displaystyle A=\pi r^2+2\pi r \left (\frac{4}{\pi r^2}\right )$

Simplifying

$\displaystyle A=\pi r^2+\frac{8}{r}$

We have the function of the area in terms of one variable. Now we compute the first derivative and equal it to zero

$\displaystyle A'=2\pi r-\frac{8}{r^2}=0$

Rearranging

$\displaystyle 2\pi r=\frac{8}{r^2}$

Solving for r

$\displaystyle r^3=\frac{4}{\pi }$

$\displaystyle r=\sqrt[3]{\frac{4}{\pi }}\approx 1.084\ feet$

Computing h

$\displaystyle h=\frac{4}{\pi \ r^2}\approx 1.084\ feet$

We can see the height and the radius are of the same size. We check if the critical point is a maximum or a minimum by computing the second derivative

$\displaystyle A''=2\pi+\frac{16}{r^3}$

We can see it will be always positive regardless of the value of r (assumed positive too), so the critical point is a minimum.

The minimum area is

$\displaystyle A=\pi(1.084)^2+\frac{8}{1.084}$

$\boxed{ A=11.07\ ft^2}$

8 0

3 years ago

Someone please help with this question :)!

Elodia [21]

I think a) would be the answer. I proceeded by elimination: the domaine of the function goes from 3 and continues to infinity, so that leaves with a) and b) as possible answers. Both have the same range and both of their functions reflect over the x axis, so we have to compare the two answer by looking at the position of the function in the graph. The function is in the first quadrant (top right corner), so the position of the function has to be at our right, which leads us to a).

3 0

3 years ago