8. Find the standard deviation, to one decimal place, of the test marks tabulated below. 41-50 51-60 61-70 71-80 81-90 Mark Frequency 5 0 10 8 2

Answer:161.56

Step-by-step explanation:

8 x5=40

8 x 7.07=56.56

1/2 x 5 x 5 x 2= 25

8 x 5=40

Add that all together

The expression which is equivalent to -10 is the option b, -3 - 7.

Explanation:

We can use subtraction and addition of integers to get the value of the given expression. We can write the given expression as;

-3 - 7 = -10 (-3 - 7)

The addition of two negative integers will always give a negative integer. When we subtract a larger negative integer from a smaller negative integer, we will get a negative integer.

If we add -3 and -7 we will get -10. This makes the option b the correct answer.

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Answer:

x=12

Step-by-step explanation:

5x = -3x+24

2x = 24

x = 12

Answer:

-x³ + 3x² - 14x + 12

Step-by-step explanation:

Area of outer rectangle = (x² + 3x - 4) * (2x - 3)

      = (x² + 3x - 4) * 2x  + (x² + 3x - 4) * (-3)

     =x²*2x + 3x *2x - 4*2x  + x² *(-3) + 3x *(-3)  - 4*(-3)

     =2x³ + 6x² - 8x - 3x² - 9x + 12

    = 2x³ + 6x² - 3x²   - 8x - 9x + 12     {Combine like terms}

    = 2x³ + 3x² - 17x + 12

Area of inner rectangle = (x² - 1)* 3x

                                       = x² *3x - 1*3x

                                       = 3x³ - 3x

Area of shaded region = area of outer rectangle - area of inner rectangle

         = 2x³ + 3x² - 17x + 12 - (3x³ - 3x)

         = 2x³ + 3x² - 17x + 12 -3x³ + 3x

        = 2x³ - 3x³ + 3x² - 17x + 3x + 12

        = -x³ + 3x² - 14x + 12

Answer:

8 feet by 28 feet by 6 feet

Step-by-step explanation:

So volume is length times width times height

It tells us that the volume is 1344 cubic feet (the water used to fill it)

And it also tells us that the height/depth (which are the same thing in this case) is 6ft

All we need now are length and width

We know that one of the sides is 3.5 times the other one. So we can just say length is x and width is 3.5x

So plugging that in, the equation becomes

[tex]3.5x*x*6=1344[/tex]

3.5 x times x is just 3.5x squared so

[tex]3.5x^2*6=1344[/tex]

       divide both sides by 6

[tex]3.5x^2=244[/tex]

       divide by 3.5

[tex]x^2 =64[/tex]

        [tex]x=\sqrt{64}[/tex]

x = 8

So that means the one side is 8 feet long and the other side is 3.5 times that, which is 28 feet long.

So the dimensions of the pool are 8 feet by 28 feet by 6 feet

There is 90% confidence that the population mean number of books read is between 9.85 and 15.55. If repeated samples are taken, 90% of them will have a sample mean between 9.85 and 15.55. There is a 90% probability that the true mean number of books read is between 9.85 and 15.55.

The survey results indicate that the mean number of books read in the past year is estimated to be 12.7, with a standard deviation of 16.6. To construct a 90% confidence interval, we can use the t-distribution and the sample size of 1014. Using the critical t-values from the table, we calculate the margin of error by multiplying the standard error (s / √n) with the t-value. Adding and subtracting the margin of error from the sample mean gives us the lower and upper bounds of the confidence interval.

The confidence interval for the mean number of books read is calculated as 12.7 ± (t-value * 16.6 / [tex]\sqrt{1014}[/tex]), which simplifies to 12.7 ± 2.58. Therefore, the confidence interval is (9.85, 15.55).

In interpretation, this means that we can be 90% confident that the true mean number of books read in the population falls between 9.85 and 15.55. If we were to repeat the survey and take different samples, 90% of those samples would produce a mean number of books read within the range of 9.85 to 15.55. The confidence interval provides a range of values within which we can reasonably estimate the true population mean.

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Answer:

Step-by-step explanation:

The area of a sector and the properties of circles bounded by a 144° arc in a circle with a radius of 8 miles can be calculated using the formula: Area of sector = (θ/360°) * π * r² where θ is the central angle of the sector and r is the radius of the circle.

In this case, the central angle is 144° and the radius is 8 miles. Plugging these values into the formula, we get: Area of sector = (144°/360°) * π * (8 miles)². Simplifying the equation, we have: Area of sector = (0.4) * π * (8 miles)².

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Answer:

Step-by-step explanation:

Answer:

44 is the awnser

Step-by-step explanation:

becuase if you were to look at the first persons work it is correct showing him solving the equasion and witch it is not 44

Answer:

Should be 9 centimeters.

Step-by-step explanation:

The level curves of the function f(x, y) = -2xy / (2^2 + y^2) in polar coordinates consist of lines θ = π/2 + kπ and θ = kπ, as well as the upper half and lower half of the unit circle depending on the sign of the function. These level curves represent the points (r, θ) where the function f(r, θ) is constant.

To describe the level curves of the function f(x, y) = -2xy / (2^2 + y^2), we can first express the function in terms of polar coordinates. Let's substitute x = r cos(θ) and y = r sin(θ) into the function:

f(r, θ) = -2(r cos(θ))(r sin(θ)) / (r^2 + (r sin(θ))^2)

Simplifying this expression, we get:

f(r, θ) = -2r^2 cos(θ) sin(θ) / (r^2 + r^2 sin^2(θ))

Now, we can further simplify this expression:

f(r, θ) = -2r^2 cos(θ) sin(θ) / (r^2(1 + sin^2(θ)))

f(r, θ) = -2 cos(θ) sin(θ) / (1 + sin^2(θ))

The level curves of this function represent the points (r, θ) in polar coordinates where f(r, θ) is constant. Let's consider a few cases:

1. When f(r, θ) = 0:

  This occurs when -2 cos(θ) sin(θ) / (1 + sin^2(θ)) = 0. Since the numerator is zero, we have either cos(θ) = 0 or sin(θ) = 0. These correspond to the lines θ = π/2 + kπ and θ = kπ, where k is an integer.

2. When f(r, θ) > 0:

  In this case, the numerator -2 cos(θ) sin(θ) is positive. For the denominator 1 + sin^2(θ) to be positive, sin^2(θ) must be positive. Therefore, the level curves lie in the regions where sin(θ) > 0, which corresponds to the upper half of the unit circle.

3. When f(r, θ) < 0:

  Similar to the previous case, the level curves lie in the regions where sin(θ) < 0, which corresponds to the lower half of the unit circle.

In summary, the level curves of the function f(x, y) = -2xy / (2^2 + y^2) in polar coordinates consist of lines θ = π/2 + kπ and θ = kπ, as well as the upper half and lower half of the unit circle depending on the sign of the function.

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Answer:

3328 cubic centimeters

Step-by-step explanation:

volume of pyramid equation:

V=(lwh)/3

V = (12·26·32) / 3

V =3328

Answer:

The answer is

[tex]9984 cm {}^{3} [/tex]

Step-by-step explanation:

The way i solved this was by using the formula to volume. I also am doing this but for me it is a bit easier. The simple formula is Width x Length x Height. Since i already have the numbers, it is easier to plug in the numbers

If "f" is function with derivative as f'(x) = √(x³ + 1), then length of graph of y = f(x) from x = 0 to x = 1.5 is (b) 2.497.

To find the length of the graph of y = f(x) from x = 0 to x = 1.5, we use the arc-length formula for a function y = f(x):

Length = ∫ᵇₐ√(1 + [f'(x)]²) dx,

Given the derivative : f'(x) = √(x³ + 1), we substitute it into the arc-length formula:

Length = [tex]\int\limits^{1.5}_{0}[/tex] √(1 + (√(x³ + 1))²) dx,

Simplifying the expression inside the square root:

We get,

Length = [tex]\int\limits^{1.5}_{0}[/tex] √(1 + x³ + 1) dx

= [tex]\int\limits^{1.5}_{0}[/tex]√(x³ + 2) dx

= 2.497.

Therefore, the correct option is (b).

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The given question is incomplete, the complete question is

Let f be a function with derivative given by f'(x) = √(x³ + 1). What is the length of the graph of y = f(x) from x = 0 to x = 1.5?

(a) 4.266

(b) 2.497

(c) 2.278

(d) 1.976

Answer:

0.28

Step-by-step explanation:

All you need to do is count.

0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30

                                                                              C

Point C sits on the point 0.28.

Quotient: The result of dividing two numbers

Explanation: Just some simple dividing and rounding

Quotient - 102.756098

Rounding - 102.76

Answer: 102.76

Answer:

XY would also be 7 centimeters which is answer D.

Step-by-step explanation:

This is a parallelogram, meaning that the adjacent sides are congruent. As well, the triangles making up the figure are congruent, so it makes sense that XY would also equal 7 centimeters.

Answer:

The first term is 10.

The second term is 16

The third term is 22.

We can see that the first term plus 6, is:

10 + 6 = 16

Then the first term plus 6 is equal to the second term.

And the second term plus 6 is:

16 + 6 = 22

Then the second term plus 6 is equal to the third term.

A) As we already found, the recursive rule is:

Aₙ = Aₙ₋₁ + 6

B) The explicit rule is:

Aₙ = A₁ + (n - 1)*6

Such that A1 is the first term, in this case A₁ = 10

Then:

Aₙ = 10 + (n - 1)*6

C)

Now we want to find A₅, then:

A₅ = 10 + (5 - 1)*6 = 34

There are 34 chairs in row 5.

D)

Here we have 17 rows, then we can have 17 terms, this means that the total number of chairs will be:

C = A₀ + A₁ + ... + A₁₆

This summation can be written as:

∑ 10 + (n - 1)*6        such that n goes from 0 to 16.

The formula  for the sum of the first N terms of a sum like this is:

S(N) = (N)*(A₁ + Aₙ)/2

Then the sum of the 17 rows gives:

S(17) = 17*(10 + (10 + (17 - 1)*6)/2 = 986 chairs.

There are total 986 chairs in the considered auditorium and there are 34 chairs in the fifth row.

A rule defined such that its definition includes itself.

Example: [tex]F(x) = F(x-1) + c[/tex] is one such recursive rule.

For this case, we're provided that:

Seats in rows are 10 in front, 16 in second, 22 in third, and so on.

10 , 16 , 22 , .....

16 - 10 = 6

22 - 16 = 6

...

So consecutive difference is 6

If we take [tex]T_i[/tex] as ith term of the series then:

[tex]T_2 - T_1 = 6\\T_3 - T_2 = 6\\T_4 - T_3 = 6 \\T_5 - T_4 = 6\\\cdots\\T_{n} - T_{n-1} = 6[/tex]

Thus, the recursive rule for the given series is [tex]T_{n} - T_{n-1} = 6[/tex] or [tex]T_n = T_{n-1} + 6[/tex]

From this recursive rule, we can deduce the explicit formula as:
[tex]T_n = T_{n-1} + 6\\T_n = T_{n-2} + 6 + 6\\\cdots\\T_n = T_{n-k} + k \times 6\\T_n = T_1 + 6(n-1)\\T_n = 10 + 6(n-1) \: \rm (as \: T_1 = 10)\\[/tex]

Thus, the explicit rule for this series is [tex]T_n = 10 + 6(n-1)[/tex]

For 5th row, putting n = 5 gives us:

[tex]T_n = 10 + 6(n-1) = 6n + 4\\T_5 = 6(5) + 4 = 34[/tex]

If the auditorium has 17 rows, then total chairs are:

[tex]T = T_1 + T_2 + \cdots + T_{17} = \sum_{n=1}^{17} T_n\\\\T = \sum_{n=1}^{17} (10 + 6(n-1))\\\\T = \sum_{n=1}^{17} (6n + 4)\\\\T = 6\sum_{n=1}^{17} n + \sum_{n=1}^{17}4 = 6\sum_{n=1}^{17} n + 4 \times 17\\\\T = 6\left( \dfrac{17(18)}{2}\right) + 68 = 918 + 68\\\\T = 986[/tex]

(it is because [tex]\sum_{k=1}^n k = 1 + 2 + \cdots + n = \dfrac{n(n+1)}{2}[/tex] )

Thus, there are total 986 chairs in the considered auditorium. There are 34 chairs in the fifth row. The recursive rule for this series is: [tex]T_n = T_{n-1} + 6[/tex] The explicit rule for this series is: [tex]T_n = 6n + 4[/tex].

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Answer:

G

Step-by-step explanation:

out of a total of 280 spinners as the overall.

3/40 were defective

280 * 3/40 = 21

Answer:

G

Step-by-step explanation:

For every 40 spinners 3 are defective

Divide amount made by 40 for numbers of groups of 40

280 ÷ 40 = 7 , then

7 × 3 = 21 ← likely defective spinners → G

The given problem is about hypothesis testing. The sample size is 40, and the proportion of students reporting their studies in the new situation (online) is the same as in the face-to-face context is 46%.

1A. The expected numbers of university students who reported the same learning experience in online and face-to-face contexts are 18.4.

1B. The degrees of freedom associated with this hypothesis test is 39.

1C. The value of the test statistic associated with this hypothesis test is approximately 0.518.

Here, the null hypothesis is H0: p = 0.46 and the alternative hypothesis is Ha: p ≠ 0.46, where p is the proportion of university students reporting the same learning experience in online and face-to-face contexts.

Here, we are interested in testing whether the proportion of students reporting an equal preference for online and face-to-face learning has changed due to the Covid-19 pandemic.

1A. Assuming the hypothesized value holds, the expected numbers of university students who reported the same learning experience in online and face-to-face contexts are 0.46 × 40 = 18.4.

1B. The degrees of freedom associated with this hypothesis test is (n - 1) where n is the sample size.

Here, n = 40.

Hence, the degrees of freedom will be 40 - 1 = 39.

1C. The value of the test statistic associated with this hypothesis test can be calculated as follows:

z = (X - μ) / σ, where X = 20,

μ = np

μ = 18.4, and

σ = √(npq)

σ = √(40 × 0.46 × 0.54)

σ ≈ 3.09.

z = (20 - 18.4) / 3.09

z ≈ 0.518

So, the value of the test statistic associated with this hypothesis test is approximately 0.518.

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Answer:

Step-by-step explanation:

Focus of parabola [tex](y-2)^2 = 4(x+3)[/tex] is (-2 , 2) .

Correct option is C .

Given, Equation of parabola  [tex](y-2)^2 = 4(x+3)[/tex]

Focus of parabola :

Standard equation of parabola : (y - k)² = 4a(x - h)

Axis of parabola : y = k

Vertex of parabola : (h, k)

Focus of parabola : (h + a, k)

Compare the equation of parabola with standard equation.

(y - k)² = 4a(x - h)

[tex](y-2)^2 = 4(x+3)[/tex]

k = 2

a = 1

h = -3

So focus of parabola:  (h + a, k).

-3 + 1 , 2

Focus of parabola = -2 , 2

Hence the correct option is C .

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Answer: w=5

Step-by-step explanation: Hope this help

Probability refers to the measure of the likelihood that a particular event will occur. It is represented as a value between 0 and 1, where 0 indicates an impossible event and 1 indicates a certain event.

The probability of not rolling a 2 on a number cube with sides numbered 1 through 6 is 5/6.

Here's why: When we roll a number cube with sides numbered 1 through 6, there are six possible outcomes, each with an equal probability of 1/6:1, 2, 3, 4, 5, 6.The probability of rolling a 2 is 1/6, which means there is only one way to roll a 2 out of the six possible outcomes. The probability of not rolling a 2 is the probability of rolling any of the other five possible outcomes. Each of these outcomes has an equal probability of 1/6. Therefore, the probability of not rolling a 2 is:1 - (1/6) = 5/6. Answer: b. 5/6.

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Given that the number cube has sides numbered 1 through 6. The probability of rolling a 2 is 1/6. The probability of not rolling a 2 on a number cube with sides numbered 1 through 6 is 5/6.

The probability of rolling any of the numbers 1, 3, 4, 5, or 6 is also 1/6 each.

The sum of the probabilities of all possible outcomes is 1.

The probability of an event happening is defined as the number of ways the event can occur, divided by the total number of possible outcomes.

The total number of possible outcomes is 6 (the numbers 1 through 6).

Thus, if the probability of rolling a 2 is 1/6, then the probability of not rolling a 2 is 1 - 1/6 = 5/6.

Therefore, the correct option is b. 5/6.

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The critical points function relative extrema and saddle points.

(a) f(x, y) = x - x2 - y2 =f(x, y) = 0: x - x² - y²= 0

(b) f(x, y) = (x + 1)(y – 2)=: x + 1 = 0 and y - 2 = 0.

(c) f(x, y) = sin(xy)= cos(xy),

(d) f(x, y) = xy(x - 1)= (0, 0) and (1, y)

(a) For the function f(x, y) = x - x² - y²

To find the critical points, to find where the gradient is zero or undefined. The gradient of f(x, y) is given by (∂f/∂x, ∂f/∂y):

∂f/∂x = 1 - 2x

∂f/∂y = -2y

Setting both partial derivatives to zero,

1 - 2x = 0 -> x = 1/2

-2y = 0 -> y = 0

The only critical point is (1/2, 0).

To determine the nature of the critical point, examine the second-order partial derivatives:

∂²f/∂x² = -2

∂²f/∂y² = -2

∂²f/∂x∂y = 0

The determinant of the Hessian matrix is Δ = ∂²f/∂x² * ∂²f/∂y² - (∂²f/∂x∂y)² = (-2)(-2) - (0)² = 4.

Since Δ > 0 and ∂²f/∂x² = -2 < 0, the critical point (1/2, 0) is a local maximum.

To sketch the level sets,  set f(x, y) to different constant values and plot the corresponding curves. For example:

f(x, y) = -1: x - x² - y² = -1

This equation represents a circle with radius 1 centered at (1/2, 0).

f(x, y) = 0: x - x² - y² = 0

This equation represents a parabolic shape that opens downward.

(b) For the function f(x, y) = (x + 1)(y - 2):

To find the critical points, we set both partial derivatives to zero:

∂f/∂x = y - 2 = 0 -> y = 2

∂f/∂y = x + 1 = 0 -> x = -1

The only critical point is (-1, 2).

To determine the nature of the critical point, we can examine the second-order partial derivatives:

∂²f/∂x² = 0

∂²f/∂y² = 0

∂²f/∂x∂y = 1

Since the second-order partial derivatives are all zero, we cannot determine the nature of the critical point based on them. We need further analysis.

To sketch the level sets,  set f(x, y) to different constant values and plot the corresponding curves. For example:

f(x, y) = 0: (x + 1)(y - 2) = 0

This equation represents two lines: x + 1 = 0 and y - 2 = 0.

(c) For the function f(x, y) = sin(xy):

To find the critical points, both partial derivatives to zero:

∂f/∂x = ycos(xy) = 0 -> y = 0 or cos(xy) = 0

∂f/∂y = xcos(xy) = 0 -> x = 0 or cos(xy) = 0

From y = 0 or x = 0, the critical points (0, 0).

When cos(xy) = 0,  xy = (2n + 1)π/2 for n being an integer. In this case,  infinitely many critical points.

To determine the nature of the critical points, we can examine the second-order partial derivatives:

∂²f/∂x² = -y²sin(xy)

∂²f/∂y² = -x²sin(xy)

∂²f/∂x∂y = (1 - xy)cos(xy)

Since the second-order partial derivatives involve the trigonometric functions sin(xy) and cos(xy), it is challenging to determine the nature of the critical points without further analysis.

To sketch the level set f(x, y) to different constant values and plot the corresponding curves.

(d) For the function f(x, y) = xy(x - 1):

To find the critical points, both partial derivatives to zero:

∂f/∂x = y(x - 1) + xy = 0 -> y(x - 1 + x) = 0 -> y(2x - 1) = 0

∂f/∂y = x(x - 1) = 0

From y(2x - 1) = 0,  y = 0 or 2x - 1 = 0. This gives us the critical points (0, 0) and (1/2, y) for any y.

From x(x - 1) = 0,  x = 0 or x = 1. These values correspond to the critical points (0, 0) and (1, y) for any y.

To determine the nature of the critical points,  examine the second-order partial derivatives:

∂²f/∂x² = 2y

∂²f/∂y² = 0

∂²f/∂x∂y = 2x - 1

For the critical point (0, 0), the second-order partial derivatives are ∂²f/∂x² = 0, ∂²f/∂y² = 0, and ∂²f/∂x∂y = -1. Based on the second partial derivative test, this critical point is a saddle point.

For the critical points (1, y) and (1/2, y) where y can be any value, the second-order partial derivatives are ∂²f/∂x² = 2y, ∂²f/∂y² = 0, and ∂²f/∂x∂y = 1. The nature of these critical points depends on the value of y.

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Answer:

mean: 3.3

median: 3

mode: 3

range: 5

Q1 = 2

Q3 = 4

IQR = 2

Step-by-step explanation:

(a) To compute P(X₁ + X₂ ≤ 1), we can list out all the possible values of X₁ and X₂ that satisfy the inequality: X₁ + X₂ ≤ 10 + 0 = 0, which is impossible, so P(X₁ + X₂ ≤ 1) = P(X₁ = 0, X₂ = 0) + P(X₁ = 1, X₂ = 0) + P(X₁ = 0, X₂ = 1) = (1/3)² + (1/3)² + (1/3)² = 1/3.

(b) The moment generating function (mgf) of X₁ is given by:

M(t) = E(etX₁) = (1/3) et0 + (1/3) et1 + (1/3) et2 = (1/3) + (1/3) et + (1/3) e2t

The domain of M(t) is the set of all values of t for which E(etX₁) exists.

(c) Let X be the sample average of {Xk}, where Xk are i.i.d random variables with the same distribution as X₁.

Then, by the linearity of expectation and the definition of X₁, we have:

E(X) = E( (X₁ + X₂ + ... + Xn)/n ) = (E(X₁) + E(X₂) + ... + E(Xn))/n = (EX₁ + EX₂ + ... + EXn)/n = X₁ = 1

From part (b), we have the mgf of X₁ as M₁(t) = (1/3) + (1/3)et + (1/3)e2t.

Then, the mgf of X is given by the formula: M(t) = E(etX) = et (X₁ + X₂ + ... + Xn)/n) = E(etX₁/n) × E(etX₂/n) × ... × E(etXn/n) = (M₁(t/n)) ⁿ = [(1/3) + (1/3) et/n + (1/3) e2t/n] ⁿ

The domain of M(t) is the set of all values of t for which E(etX) exists.

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