Please help out explanation need it

Let x(t) denote the amount of salt (in kg) in the tank at time t. The tank starts with 18 kg of salt, so x (0) = 18.

The solution is drained from the tank at a rate of 90 L/min, so that the amount of salt in the tank changes according to the differential equation

dx(t)/dt = - (x(t) kg)/(9000 L) × (90 L/min) = -1/100 x(t) kg/min

or, more succintly,

x' = -1/100 x

This equation is separable as

dx/x = -1/100 dt

Integrating both sides gives

∫ dx/x = -1/100 ∫ dt

ln|x| = -1/100 t + C

x = exp(-1/100 t + C )

x = C exp(-t/100)

(a) Using the initial condition x (0) = 18, we find

18 = C exp(0)   ==>   C = 18

so that

x(t) = 18 exp(-t/100)

(b) After 20 minutes, we have

x (20) = 18 exp(-20/100) = 18 exp(-1/5) ≈ 14.74

so the tank contains approximately 14.74 kg of salt after this time.

RHS

[tex]\\ \sf\longmapsto \frac{2 \tan( \theta) }{ \sin(2 \theta) } \\ \\ \sf\longmapsto \frac{ \frac{2 \sin( \theta) }{2 \cos( \theta) } }{ \sin(2 \theta) } \\ \\ \sf\longmapsto \frac{1}{ \cos {}^{2} ( \theta) } \\ \\ \sf\longmapsto {sec}^{2} \theta[/tex]

Answer:

A

Step-by-step explanation:

We have,

[tex]a:b=3:6,a+b=96[/tex]

Introduce variable [tex]x[/tex] such that [tex]a=3x,b=6x[/tex]

The sum [tex]a+b=96[/tex] is therefore [tex]9x=96\implies x=10.\overline{6}[/tex]

So,

[tex]a=3\cdot10.\overline{6}=\boxed{32}[/tex] (sadia's age)

[tex]b=6\cdot10.\overline{6}=\boxed{64}[/tex] (father's age)

Hope this helps :)

Answer:

.73 per pound

Step-by-step explanation:

Take the total cost and divide by the number of pounds

4.38/ 6

.73 per pound

Can you post an image of the map?

Answer:

i believe that the answer is 38 please trust me

Answer:

60

Step-by-step explanation:

15kilometers into 1 hour

60 minutes in 1 hour

so Amir ran 15 kilometers in 60 minutes

Answer:

0.25 km

step explanation:

that was the anwser on khan

Assuming the car's speed [tex]\frac{630}{14}=45\mathrm{mph}[/tex] does not change, the car will travel [tex]45\cdot42=\boxed{1890}[/tex] miles.

Hope this helps :)

Answer:

12.6

Step-by-step explanation:

Length of arc=(2*pi*r)*(theta/360)

Length of arc=(2*12*pi)*(1/6)=12.6

2=4x+y

y=2-4x

Александр Мазепов

Step-by-step explanation:

Step 1:  Solve for y

[tex]2 = 4x + y[/tex]

[tex]2 - 4x = 4x + y - 4x[/tex]

[tex]y = 2 - 4x[/tex]

Step 2:  Solve for x

[tex]2 - 2 - 4x = 0 - 2[/tex]

[tex]-4x / -4 = -2 / -4[/tex]

[tex]x = 1/2[/tex]

Step 3:  Solve for y

[tex]y = 2 - 4(0)[/tex]

[tex]y = 2[/tex]

Step 4:  Graph the equation

Graph the x-intercept, (1/2, 0), the y-intercept, (0, 2) and draw a line between them.  Look at the attached picture for the graph:

Answer: 240 minutes

Step-by-step explanation:

Concept:

Here, we need to know the idea of unit conversion.

Unit conversion is the conversion between different units of measurement for the same quantity, typically through multiplicative conversion factors.

1 hour = 60 minutes

Solve:

1 hour = 60 minutes

4 hours = 4 × 60 = 240 minutes

Hope this helps!! :)

Please let me know if you have any questions

Answer:

325 pencils, 650 markers, 975 pens.

1099.56m² is the surface area of a cylinder that has a radius of 7 m and a height of 18 m.

Answer:

20 girls

Step-by-step explanation:

boys: girls

3          5

There are 12 boys

12/3 = 4

Multiply each side by 4

boys: girls

3*4      5*4

12         20

Answer:

20 girls

Step-by-step explanation:

Divide 12 by 3 : 12/3 = 4

Multiply 4 by 5 : 4*5 = 20

Let's use Gaussian elimination. Consider the augmented matrix,

[tex]\left[\begin{array}{ccc|ccc}1 & -1 & -1 & 1 & 0 & 0\\-1 & 2 & 3 & 0 & 1 & 0\\1 & 1 & 4 & 0 & 0 & 1\end{array}\right][/tex]

• Add row 1 to row 2, and add -1 (row 1) to row 3:

[tex]\left[\begin{array}{ccc|ccc}1 & -1 & -1 & 1 & 0 & 0\\0 & 1 & 2 & 1 & 1 & 0\\0 & 2 & 5 & -1 & 0 & 1\end{array}\right][/tex]

• Add -2 (row 2) to row 3:

[tex]\left[\begin{array}{ccc|ccc}1 & -1 & -1 & 1 & 0 & 0\\0 & 1 & 2 & 1 & 1 & 0\\0 & 0 & 1 & -3 & -2 & 1\end{array}\right][/tex]

• Add -2 (row 3) to row 2:

[tex]\left[\begin{array}{ccc|ccc}1 & -1 & -1 & 1 & 0 & 0\\0 & 1 & 0 & 7 & 5 & -2\\0 & 0 & 1 & -3 & -2 & 1\end{array}\right][/tex]

• Add row 2 and row 3 to row 1:

[tex]\left[\begin{array}{ccc|ccc}1 & 0 & 0 & 5 & 3 & -1\\0 & 1 & 0 & 7 & 5 & -2\\0 & 0 & 1 & -3 & -2 & 1\end{array}\right][/tex]

So the inverse is

[tex]\begin{bmatrix}1&-1&-1\\-1&2&3\\1&1&4\end{bmatrix}^{-1} = \boxed{\begin{bmatrix}5&3&-1\\7&5&-2\\-3&-2&1\end{bmatrix}}[/tex]

Answer:

The answer is C

Step-by-step explanation:

PLATO

Answer:

It's letter b

Step-by-step explanation:

I hope this help

Answer:

the third option (a=1, h=0, k=6)

Step-by-step explanation:

if I understand correctly what your teacher wants from you, then you need find a (the factor of x² in the equation) and the vertex (turnaround point) of the parabola represented by such a quadratic equation.

the vertex point coordinates are called (h, k).

the general form of such an equation equation is

y = ax² + bx + c

so, we have a right away : a=1

now we can make this quickly by using common sense, or a bit more complex by going through mathematical formulas.

the fast, practical way is to know that y=x² is the very basic parabola with its vertex at (0, 0).

y = x² + 6 is simply the same parabola just lifted up (y direction) by 6 units, that makes the vertex (0, 6).

in pure theory, though, we need to find the transformation from the general y = ax² + bx + c form to

y = a(x - h)² + k

we see right away that k = f(h) = h² + 6

y = a(x² - 2xh + h²) + k

a=1

y = x² - 2xh + h² + k = x² - 2xh + h² + h² + 6 =

= x² - 2xh + 2h² + 6

comparing with y = x² + 6

we know that

-2×h = 0

as we have no term with just x.

=> h = 0

2h² + 6 = k

2×0² + 6 = 6 = k

9514 1404 393

Answer:

Step-by-step explanation:

In the parallelogram shown, angle B is the supplement of angle DAB:

  ∠B = 180° -77°37' = 102°23'

Angle ACB is the difference of angles 77°37' and 27°8', so is 50°29'.

Now, we know the angles and one side of triangle ABC. We can use the law of sines to solve for the other two sides.

  BC/sin(A) = AB/sin(C)

  AD = BC = AB·sin(A)/sin(C) = (169 lb)sin(27°8')/sin(50°29') ≈ 99.91 lb

 AC = AB·sin(B)/sin(C) = (169 lb)sin(102°23')/sin(50°29') ≈ 213.97 lb

Answer:

D Replace on equation with sum /difference of both equations

The systems are still the same

Step-by-step explanation:

5x + y = 3

4x - 7y = 8

Subtract the second equation from the first

5x + y = 3

-(4x - 7y = 8)

-----------------

x    +8y = -5

The second equation in system B is the first equation in system a minus the second equation in system A

We added the same thing to each side of the equation so the the system is still the same

Answer:

Step-by-step explanation:

A = (2)(3.14)(2)(4) + (2)(3.14)(2^2)

A = 75.36 in

Answer:

None of them

Step-by-step explanation:

n+3<12

(Subtract 3 from both sides)

n<9

(n is less than 9, so n is everything left of 9)

(the inequality symbols: > and < are an open dot)

(none of the choices display n<9 with an open dot, so none of the options are correct)

(if you meant < with a line underneath it, then the dot would be filled, and the answer would be D)

Answer:

Quadrant 4

Step-by-step explanation:

If the given angle was positive, then we go clockwise.

But it's negative so we go counterclockwise.

An alternative way of graphing

Quadrant 1 is 0-90°

Quadrant 2 is 90-180°

Quadrant 3 is 180-270°

Quadrant 4 is 270-360°

Subtract the given angle by 360 until no longer possible

750 - 360 = 390     390 - 360 = 30

Remember that this was originally a negative angle

Instead of going clockwise to quadrant 1, we go counterclockwise to quadrant 4, ending up at 330°

Answer:

3

Step-by-step explanation:

3 = 9 \:th \\ 1 = 3 \\ 3 \times 3 = 9 \\ 9 \div 3 = 3 \\ so \: that \: answer \: is \: 3

Answer:

1/3

Step-by-stepi

Answer:

4 3/4 cups PLEASE MARK ME BRAINLIEST

Step-by-step explanation:

Bowl = 8 cups

Armando first used 2 1/2 cups of flour. So, we need to do 8 - 2 1/2.

8 - 2 1/2 = 8/1 - 5/2

Find the common denominator:

8/1 - 5/2 = 8 x 2/1 x 2 - 5 x 1/2 x 1 = 16/2 - 5/2

Find the final answer:

16/2 - 5/2 = 11/2 = 5 1/2

Then, Armando used 3/4 cups of sugar. So, we need to do 5 1/2 - 3/4.

5 1/2 - 3/4 = 11/2 - 3/4

Find the common denominator:

11/2 - 3/4 = 11 x 2/2 x 2 - 3 x 1/4 x 1 = 22/4 - 3/4

Find the final answer:

22/4 - 3/4 = 19/4 = 4 3/4

Finally, Armando used 1/3 cup of butter. So, we need to do 4 3/4 - 1/3.

4 3/4 - 1/3 = 19/4 - 1/3

Find the common denominator:

19/4 - 1/3 = 19 x 3/4 x 3 - 1 x 4/3 x 4 = 57/4 - 4/12

Find the final answer:

57/4 - 4/12 = 53/12 = 4 5/12

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Answer:

The answer is 21.98. I just took area of the whole circle and subtracted it with the area of two circles in it

Answer:

21. 99

Step-by-step explanation:

[tex]s = \pi \times {r}^{2} \\ s1 = 3.14 \times 9 = 28.27 \\ s2 = 3.14 \times 1 = 3.14 \\ a = 28.27 - (3.14 \times 2) = 28.27 - 6.28 = 21.99[/tex]

Answer:

a) The error bound of the confidence interval is of 0.66.

b) The confidence interval will be narrower.

Step-by-step explanation:

Question a:

We have to find the margin of error. Considering that we have the standard deviation for the sample, the t-distribution is used.

The first step to solve this problem is finding how many degrees of freedom,which is the sample size subtracted by 1. So

df = 71 - 1 = 70

95% confidence interval

Now, we have to find a value of T, which is found looking at the t table, with 70 degrees of freedom(y-axis) and a confidence level of [tex]1 - \frac{1 - 0.95}{2} = 0.975[/tex]. So we have T = 1.9944

The margin of error is:

[tex]M = T\frac{s}{\sqrt{n}}[/tex]

In which s is the standard deviation of the sample and n is the size of the sample.

For this problem, [tex]s = 2.8, n = 71[/tex]. So

[tex]M = T\frac{s}{\sqrt{n}} = 1.9944\frac{2.8}{\sqrt{71}} = 0.66[/tex]

The error bound of the confidence interval is of 0.66.

b. What will happen to the level of confidence obtained if 1,000 male Swedes are surveyed instead of 48? Why?

The margin of error is inversely proportional to the square root of the sample size, so increasing the sample size leads to a smaller margin  of error and a narrower confidence interval.