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2 years ago

PLEASE HELP ME!! I WILL GIVE BRAINLIEST TO THE FIRST TO HELP ME, AS WELL AS 5 STARS AND A THANK YOU!!!!

Mathematics

1 answer:

viktelen [127]2 years ago

3 0

Answer:

Step-by-step explanation:

Its 3 times 3 times 3

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How long does it take you and students 2 and 3 to clean up a 12 ft. X 12 ft wall covered in graffiti? Besides the answer (be spe

Ostrovityanka [42]

Answer:

At a combined speed of 6 in/min, it takes us 24 mins to clean the wall

Step-by-step explanation:

Since the question did not provide the speed with which each student cleans, we can make assumptions. This is so that we can solve the question before us

Assuming student 1 cleans at a speed of 2 inches per minute, student 2 cleans at a speed of 2½ inches per minute & student 3 cleans at a speed of 1½ inches per minute.

Let's list the parameters we have:

Height of wall (h) = 12 ft, Speed (student 1) = 2 in/min, Speed (student 2) = 2½ in/min, Speed (student 3) = 1½ in/min

Speed of cleaning wall = Height of wall ÷ Time to clean wall

Time to clean wall (t) = Height of wall ÷ Speed of cleaning wall

since students 1, 2 and 3 are working together, we will add their speed together; v = (2 + 2½ + 1½) = 6 in/min

1 ft = 12 in

Time (t) = h ÷ v = (12 * 12) ÷ 6 = 144 ÷ 6

Time (t) = 24 mins

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3 years ago

How do I find out how to solve a triangle

Murljashka [212]

What exactly are you asking. Are you asking for area or perimeter?

5 0

3 years ago

Read 2 more answers

Problem 4: Let F = (2z + 2)k be the flow field. Answer the following to verify the divergence theorem: a) Use definition to find

Viktor [21]

Given that you mention the divergence theorem, and that part (b) is asking you to find the downward flux through the disk $x^2+y^2\le3$ , I think it's same to assume that the hemisphere referred to in part (a) is the upper half of the sphere $x^2+y^2+z^2=3$ .

a. Let $C$ denote the hemispherical <u>c</u>ap $z=\sqrt{3-x^2-y^2}$ , parameterized by

$\vec r(u,v)=\sqrt3\cos u\sin v\,\vec\imath+\sqrt3\sin u\sin v\,\vec\jmath+\sqrt3\cos v\,\vec k$

with $0\le u\le2\pi$ and $0\le v\le\frac\pi2$ . Take the normal vector to $C$ to be

$\vec r_v\times\vec r_u=3\cos u\sin^2v\,\vec\imath+3\sin u\sin^2v\,\vec\jmath+3\sin v\cos v\,\vec k$

Then the upward flux of $\vec F=(2z+2)\,\vec k$ through $C$ is

$\displaystyle\iint_C\vec F\cdot\mathrm d\vec S=\int_0^{2\pi}\int_0^{\pi/2}((2\sqrt3\cos v+2)\,\vec k)\cdot(\vec r_v\times\vec r_u)\,\mathrm dv\,\mathrm du$

$\displaystyle=3\int_0^{2\pi}\int_0^{\pi/2}\sin2v(\sqrt3\cos v+1)\,\mathrm dv\,\mathrm du$

$=\boxed{2(3+2\sqrt3)\pi}$

b. Let $D$ be the disk that closes off the hemisphere $C$ , parameterized by

$\vec s(u,v)=u\cos v\,\vec\imath+u\sin v\,\vec\jmath$

with $0\le u\le\sqrt3$ and $0\le v\le2\pi$ . Take the normal to $D$ to be

$\vec s_v\times\vec s_u=-u\,\vec k$

Then the downward flux of $\vec F$ through $D$ is

$\displaystyle\int_0^{2\pi}\int_0^{\sqrt3}(2\,\vec k)\cdot(\vec s_v\times\vec s_u)\,\mathrm du\,\mathrm dv=-2\int_0^{2\pi}\int_0^{\sqrt3}u\,\mathrm du\,\mathrm dv$

$=\boxed{-6\pi}$

c. The net flux is then $\boxed{4\sqrt3\pi}$ .

d. By the divergence theorem, the flux of $\vec F$ across the closed hemisphere $H$ with boundary $C\cup D$ is equal to the integral of $\mathrm{div}\vec F$ over its interior:

$\displaystyle\iint_{C\cup D}\vec F\cdot\mathrm d\vec S=\iiint_H\mathrm{div}\vec F\,\mathrm dV$

We have

$\mathrm{div}\vec F=\dfrac{\partial(2z+2)}{\partial z}=2$

so the volume integral is

$2\displaystyle\iiint_H\mathrm dV$

which is 2 times the volume of the hemisphere $H$ , so that the net flux is $\boxed{4\sqrt3\pi}$ . Just to confirm, we could compute the integral in spherical coordinates:

$\displaystyle2\int_0^{\pi/2}\int_0^{2\pi}\int_0^{\sqrt3}\rho^2\sin\varphi\,\mathrm d\rho\,\mathrm d\theta\,\mathrm d\varphi=4\sqrt3\pi$

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3 years ago

How many kilometers can that tortoise walk in 1 hour

vfiekz [6]

5 kilometers

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6 0

2 years ago

What are the solutions to the equation?<br> 7x^3=28x

11Alexandr11 [23.1K]

7x³ = 28x is our equation. We want its solutions.

When you have x and different powers, set the whole thing equal to zero.

7x³ = 28x

7x³ - 28x = 0

Now notice there's a common x in both terms. Let's factor it out.

x (7x² - 28) = 0

As 7 is a factor of 7 and 28, it too can be factored out.

x (7) (x² - 4) = 0

We can further factor x² - 4. We want a pair of numbers that multiply to 4 and whose sum is zero. The pairs are 1 and 4, 2 and 2. If we add 2 and -2 we get zero.

x (7) (x - 2) (x + 2) = 0

Now we use the Zero Product Property - if some product multiplies to zero, so do its pieces.

x = 0 -----> so x = 0

7 = 0 -----> no solution

x - 2 = 0 ----> so x = 2 after adding 2 to both sides

x + 2 = 0 ---> so = x - 2 after subtracting 2 to both sides

Thus the solutions are x = 0, x = 2, x = -2.

6 0

3 years ago