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3 years ago

What is 4 divide by 2

Mathematics

1 answer:

levacccp [35]3 years ago

5 0

Answer:

Step-by-step explanation:

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John works two jobs. As a security guard he earns $8.50 per hour. As a landscaper he earns $14 per hour. One week John worked a

Rashid [163]

Answer:

John work as a security guard job 27 hours and as a landscaper 33 hours.

Step-by-step explanation:

Given:

John works two jobs.

As a security guard he earns $8.50 per hour and as a landscaper he earns $14 per hour.

One week John worked a total of 60 hours and earned $691.50.

Now, to find hours he work at each job.

Let the job of security guard be $x$ hours.

And the job of landscaper be $y$ hours.

So, the total hours John worked in a week:

$x+y=60.$

⇒ $y=60-x.$ ............( 1 )

Now, the money earned by John in a week:

$8.50x+14y=691.50$

Putting the equation ( 1 ) in the place of $y$ :

⇒ $8.50x+14(60-x)=691.50$

⇒ $8.50x+840-14x=691.50$

Moving variables on one side and the other we get:

⇒ $840-691.50=14 x-8.50x$

⇒ $148.50=5.50x$

Dividing both sides by 5.50 we get:

⇒ $27=x$

As a security guard job he worked 27 hours.

Putting the value of in $x$ equation ( 1 ) we get:

$y=60-27$

⇒ $y=33.$

As a landscaper he worked 33 hours.

Therefore, John work as a security guard job 27 hours and as a landscaper 33 hours.

5 0

3 years ago

Use the Divergence Theorem to evaluate S F · dS, where F(x, y, z) = z2xi + y3 3 + sin z j + (x2z + y2)k and S is the top half of

GenaCL600 [577]

Close off the hemisphere $S$ by attaching to it the disk $D$ of radius 3 centered at the origin in the plane $z=0$ . By the divergence theorem, we have

$\displaystyle\iint_{S\cup D}\vec F(x,y,z)\cdot\mathrm d\vec S=\iiint_R\mathrm{div}\vec F(x,y,z)\,\mathrm dV$

where $R$ is the interior of the joined surfaces $S\cup D$ .

Compute the divergence of $\vec F$ :

$\mathrm{div}\vec F(x,y,z)=\dfrac{\partial(xz^2)}{\partial x}+\dfrac{\partial\left(\frac{y^3}3+\sin z\right)}{\partial y}+\dfrac{\partial(x^2z+y^2)}{\partial k}=z^2+y^2+x^2$

Compute the integral of the divergence over $R$ . Easily done by converting to cylindrical or spherical coordinates. I'll do the latter:

$\begin{cases}x(\rho,\theta,\varphi)=\rho\cos\theta\sin\varphi\\y(\rho,\theta,\varphi)=\rho\sin\theta\sin\varphi\\z(\rho,\theta,\varphi)=\rho\cos\varphi\end{cases}\implies\begin{cases}x^2+y^2+z^2=\rho^2\\\mathrm dV=\rho^2\sin\varphi\,\mathrm d\rho\,\mathrm d\theta\,\mathrm d\varphi\end{cases}$

So the volume integral is

$\displaystyle\iiint_Rx^2+y^2+z^2\,\mathrm dV=\int_0^{\pi/2}\int_0^{2\pi}\int_0^3\rho^4\sin\varphi\,\mathrm d\rho\,\mathrm d\theta\,\mathrm d\varphi=\frac{486\pi}5$

From this we need to subtract the contribution of

$\displaystyle\iint_D\vec F(x,y,z)\cdot\mathrm d\vec S$

that is, the integral of $\vec F$ over the disk, oriented downward. Since $z=0$ in $D$ , we have

$\vec F(x,y,0)=\dfrac{y^3}3\,\vec\jmath+y^2\,\vec k$

Parameterize $D$ by

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

where $0\le u\le 3$ and $0\le v\le2\pi$ . Take the normal vector to be

$\dfrac{\partial\vec r}{\partial v}\times\dfrac{\partial\vec r}{\partial u}=-u\,\vec k$

Then taking the dot product of $\vec F$ with the normal vector gives

$\vec F(x(u,v),y(u,v),0)\cdot(-u\,\vec k)=-y(u,v)^2u=-u^3\sin^2v$

So the contribution of integrating $\vec F$ over $D$ is

$\displaystyle\int_0^{2\pi}\int_0^3-u^3\sin^2v\,\mathrm du\,\mathrm dv=-\frac{81\pi}4$

and the value of the integral we want is

(integral of divergence of F) - (integral over D) = integral over S

==> 486π/5 - (-81π/4) = 2349π/20

5 0

3 years ago

A clinical trial tests a method designed to increase the probability of conceiving a girl. In the study 335335 babies were born

strojnjashka [21]

Answer:

The 99% confidence interval estimate of the percentage of girls born is (74.37%, 85.63%).

Usually, 50% of the babies are girls. This confidence interval gives values considerably higher than that, so the method to increase the probability of conceiving a girl appears to be very effective.

Step-by-step explanation:

Confidence Interval for the proportion:

In a sample with a number n of people surveyed with a probability of a success of $\pi$ , and a confidence level of $1-\alpha$ , we have the following confidence interval of proportions.

$\pi \pm z\sqrt{\frac{\pi(1-\pi)}{n}}$

In which

z is the zscore that has a pvalue of $1 - \frac{\alpha}{2}$ .

For this problem, we have that:

$n = 335, \pi = \frac{268}{335} = 0.8$

99% confidence level

So $\alpha = 0.01$ , z is the value of Z that has a pvalue of $1 - \frac{0.01}{2} = 0.995$ , so $Z = 2.575$ .

The lower limit of this interval is:

$\pi - z\sqrt{\frac{\pi(1-\pi)}{n}} = 0.8 - 2.575\sqrt{\frac{0.8*0.2}{335}} = 0.7437$

The upper limit of this interval is:

$\pi + z\sqrt{\frac{\pi(1-\pi)}{n}} = 0.8 + 2.575\sqrt{\frac{0.8*0.2}{335}} = 0.8563$

For the percentage:

Multiplying the proportions by 100.

The 99% confidence interval estimate of the percentage of girls born is (74.37%, 85.63%).

Usually, 50% of the babies are girls. This confidence interval gives values considerably higher than that, so the method to increase the probability of conceiving a girl appears to be very effective.

7 0

3 years ago

The equation y = 36 + 18x models the relationship

wariber [46]

Answer:

Option B) The height, in inches, of a typical apple tree

Step-by-step explanation:

Let

x----> the number of years, after the tree was planted

y ---> the height in inches, of a typical golden delicious apple tree

we have

$y=36+18x$

Remember that

The y-intercept is the value of y when the value of x is equal to zero

In this problem

The y-intercept is the height of the tree when it was planted (x=0)

8 0

3 years ago

Carly can ride her bicycle 6000 meters in 15 minutes how far can she ride her bicycle in two minutes

Gala2k [10]

C. 800 Meters hope I helped

5 0

3 years ago

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