If piece of cake has area of 100 in² and sweeps angle of 50°, then the radius of the cake is 15.13 inches.
The area of the piece of cake is given as 100 square inches and
The piece of cake sweeps out an angle of 50 degrees, we have to find the radius of the cake;
We know that "Area" of a sector of a circle is given as : A = (θ/360)πr²,
where A = area of the sector, θ is = angle swept by sector, and r is radius of circle,
We know that area of "piece-of-cake" is = 100 square inches and
The "angle-swept' by the piece is = 50 degrees.
Substituting the values in area of sector formula,
We get,
⇒ 100 = (50/360)πr²,
⇒ r² = (100 × 360)/(50π)
⇒ r ≈ 15.13,
Therefore, the radius of the cake is approximately 15.13 inches.
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If f(x)=3x² -2 and g(x) = 2x+4, find (f - g)(x) pretty please?
Answer:
3x^2-2x-6
Step-by-step explanation:
So first i paid attention in class
second apply to my homework
third step apply too your
<33 ur welcome lol
Find the sum of the convergent series by using a well-known function. (Round your answer to four decimal places.) [infinity] (−1)n + 1 1 7nn n = 1
Answer:
Here is the full question:
Find the sum of the convergent series by using a well-known function. (Round your answer to four decimal places.) Σ_(n=1)^∞ (-1)^n+1 1/7^n n
Step-by-step explanation:
Σ_(n=1)^∞ (-1)^n+1 1/7^n n
We will use the function In (1 + x)
We will now give a power series expansion of the function while it is centered at x=0
This will give us In (1 + x) = Σ_(n=1)^∞\((-1)^{n+1}\)\(\frac{x^{n} }{n}\)
Note that x= 1/7
Now let us equate the two equations
Σ_(n=1)^∞\((-1)^{n+1}\)\(\frac{1}{7^{n}n }\) = ㏑(1 + x)|\(_{x = \frac{1}{7} }\) = ㏑\(\frac{8}{7}\)
Sum of the series will give ㏑\(\frac{8}{7}\)
Given m|n, find the value of x.
t
xo
>m
53°
Answer:
32 degrees goto the x vaule
Assume that females have pulse rates that are normally distributed with a mean of μ = 76.0 beats per
minute and a standard deviation of o= 12.5 beats per minute. Complete parts (a) through (c) below.
...
a. If 1 adult female is randomly selected, find the probability that her pulse rate is less than 80 beats per
minute.
The probability is
(Round to four decimal places as needed.)
b. If 25 adult females are randomly selected, find the probability that they have pulse rates with a mean
less than 80 beats per minute.
The probability is.
(Round to four decimal places as needed.)
c. Why can the normal distribution be used in part (b), even though the sample size does not exceed 30?
OA. Since the distribution is of individuals, not sample means, the distribution is a normal distribution
for any sample size.
OB. Since the mean pulse rate exceeds 30, the distribution of sample means is a normal distribution
for any sample size.
OC. Since the distribution is of sample means, not individuals, the distribution is a normal distribution
for any sample size.
OD. Since the original population has a normal distribution, the distribution of sample means is a
normal distribution for any sample size.
The original population has a normal distribution, the distribution of sample means is a normal distribution for any sample size."
a. To find the probability that a randomly selected female has a pulse rate less than 80 beats per minute, we need to standardize the value using the formula z = (x - μ) / σ, where x is the pulse rate we are interested in, μ is the mean pulse rate, and σ is the standard deviation. Thus, we have:
z = (80 - 76) / 12.5 = 0.32
Using a standard normal distribution table or a calculator, we can find that the probability of a z-score less than 0.32 is approximately 0.6255. Therefore, the probability that a randomly selected female has a pulse rate less than 80 beats per minute is:
P(z < 0.32) = 0.6255
b. Since we are dealing with a sample size of 25 females, we can use the central limit theorem, which states that the distribution of sample means will be approximately normal with a mean of μ and a standard deviation of σ / sqrt(n), where n is the sample size.
In this case, we have:
μ = 76.0
σ = 12.5
n = 25
Therefore, the standard deviation of the distribution of sample means is:
σ / sqrt(n) = 12.5 / sqrt(25) = 2.5
To find the probability that 25 randomly selected females have a mean pulse rate less than 80 beats per minute, we need to standardize the value using the formula z = (X- μ) / (σ / sqrt(n)), where X is the sample mean.
Thus, we have:
z = (80 - 76) / (2.5) = 1.6
Using a standard normal distribution table or a calculator, we can find that the probability of a z-score less than 1.6 is approximately 0.9452. Therefore, the probability that 25 randomly selected females have a mean pulse rate less than 80 beats per minute is:
P(z < 1.6) = 0.9452
c. The normal distribution can be used in part (b) because we are dealing with the distribution of sample means, not individual pulse rates. The central limit theorem states that the distribution of sample means will be approximately normal regardless of the sample size, as long as the sample size is sufficiently large (typically, n ≥ 30). In this case, we have a sample size of 25, which is smaller than 30, but we can still use the normal distribution approximation because the population distribution is assumed to be normal.
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What is the equation of the following line? Be sure to scroll down first to see all answer options.
A.
y = - x
B.
y = -2x
C.
y = 2x
D.
y = x
E.
y = -4x
F.
y = - x
Answer:
The answer is option FStep-by-step explanation:
Equation of a line is y = mx + c
where
m is the slope
c is the y intercept
To calculate the equation of the line first find the slope
Slope of the line using points
(0 , 0) and (4 , -2) is
\(m = \frac{ - 2 - 0}{4 - 0} = \frac{ - 2}{4} = - \frac{1}{2} \)
Now use the formula
y - y1 = m(x - x1) to find the equation of the line using any of the points
Using point (0,0)
That's
\(y - 0 = - \frac{ 1}{2} (x - 0)\)
The final answer is
\(y = - \frac{1}{2} x\)
Hope this helps you
Answer:
F
Step-by-step explanation:
how would someone use the cross product property on an equation with 3 different values instead of two? I provided an example image
Using the cross product for the proff of Pythagoras theorem, the correct step is
By the cross product property, AB² = BC multiplied by BD
What is cross product propertyThe cross product property is typically used to solve equations with two values, where the product of the extremes (the outer terms) is equal to the product of the means (the inner terms).
For the similar triangles, the ratio is as follows
BD / BA = BA / BC
BA² = BD * BC
and AB = BA, hence
BA² = BD * BC
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Kate and Isabelle do some fundraising for their sporting team. Together they raised $600. Kate raised $272 more than Isabelle.
1. Write an equation to represent the total amount of money the girls raised. Do not include any spaces when typing your equation.
Answer:
x + x - 272 = 600
Step-by-step explanation:
Let the amount raised by Kate by x and let the amount raised by Isabelle be y.
Now, we are told that Kate raised $272 more than Isabelle.
Thus, since amount raised by Kate is x, then amount raised by Isabelle is x - 272. We are told that together they raised $600.
Thus;
x + x - 272 = 600
Thus;
equation to represent the total amount of money the girls raised is;
x + x - 272 = 600
The length of a rectangle sign is 3 times it’s width, if the signs perimeter is 16 inches, what is the signs area
PLZ HELP !!
Max deposited $1,300 into an account that pays 4.5% interest, compounded daily. At end of six years he has a balance of ?
Answer:
The final balance is $1,692.94.
The total compound interest is $392.94.
Step-by-step explanation:
1,300 x 0.045=___ x 6
For what value of ‘K’ will the following pair of linear equations are inconsistent 3x+ 4y=1 and (2k-1) x+(k-1)y=2k+1
Answer: k=(1/5)
Step-by-step explanation:
What is the exact value of cos(-60)?
-sqrt(3)/2
-1/2
1/2
sqrt(3)/2
Answer:
1/2
Step-by-step explanation:
Look for the angle of -60, you will see the coordinate (1/2,-sqrt3/2)
The cosine function is the x value of each coordinate of the unit circle
Let me know in the comments if you have any questions! If you could mark this answer as the brainliest I would greatly appreciate it! :D
Answer:
Step-by-step explanation:
c 1/2
Solve x2 - 3x = -8 using the quadratic formula.
Answer:
No solutions
Step-by-step explanation:
\(\frac{-b ± \sqrt{b^2-4ac} }{2a}\)
Add 8 on both sides to make it into the form ax^2 + bx + c = 0
x^2 - 3x + 8 = -8 + 8
x^2 - 3x + 8 = 0
Now it is in the correct form, we can plug our numbers in.
a: 1
b: -3
c: 8
\(\frac{3 ± \sqrt{-3^2 - 4(1)(8)} }{2(1)}\)
\(\frac{3 ± \sqrt{-23} }{2(1)}\)
Because the discriminant, or b^2 - 4ac is negative, there are no solutions.
Algebra Question
Let v = (-7,6,-6) and w = (-5,-3,-6) be vectors in R^3. Find the orthogonal projection of v onto w.
Answer:
Projection on w: (-54/14, -159/70, -159/35)
I have the correct answer but I don't know how they got it.
The orthogonal projection of vector v onto vector w in R^3 is (-54/14, -159/70, -159/35).
To find the orthogonal projection of v onto w, we need to calculate the scalar projection of v onto w and multiply it by the unit vector of w. The scalar projection of v onto w is given by the formula:
proj_w(v) = (v⋅w) / (w⋅w) * w
where ⋅ denotes the dot product.
Calculating the dot product of v and w:
v⋅w = (-7)(-5) + (6)(-3) + (-6)(-6) = 35 + (-18) + 36 = 53
Calculating the dot product of w with itself:
w⋅w = (-5)(-5) + (-3)(-3) + (-6)(-6) = 25 + 9 + 36 = 70
Now, substituting these values into the formula, we have:
proj_w(v) = (53/70) * (-5,-3,-6) = (-54/14, -159/70, -159/35)
Therefore, the orthogonal projection of v onto w is (-54/14, -159/70, -159/35).
In simpler terms, the orthogonal projection of v onto w can be thought of as the vector that represents the shadow of v when it is cast onto the line defined by w. It is calculated by finding the component of v that aligns with w and multiplying it by the direction of w. The resulting vector (-54/14, -159/70, -159/35) lies on the line defined by w and represents the closest point to v along that line.
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Magic Realm, Inc., has developed a new fantasy board game. The company sold 15,000 games last year at a selling price of $20 per game. Fixed costs associated with the game total $182,000 per year, and variable costs are $6 per game. Production of the game is entrusted to a printing contractor. Variable costs consist mostly of payments to this contractor.
Required:
1) Prepare a contribution format income statement for the game last year and compute the degree of operating leverage.
2) Management is confident that the company can sell 18,000 games next year (an increase of 3,000 games, or 20%, over last year).
Compute:
a) The expected percentage increase in net operating income for next year.
b) The expected total dollar net operating income for next year.
The expected total dollar net operating Income for next year = $70,000
1) The contribution format income statement for the game last year, and the degree of operating leverage is computed below:
Contribution format income statement for the game last year Sales (15,000 × $20) = $300,000
Variable expenses (15,000 × $6) = $90,000
Contribution margin = $210,000
Fixed expenses = $182,000Net operating income = $28,000
Degree of operating leverage = Contribution margin / Net operating income= $210,000 / $28,000= 7.5 2)
The expected percentage increase in net operating income for next year:
The expected sales in next year = 18,000
games selling price per game = $20
Therefore, Total sales revenue = 18,000 × $20 = $360,000
Variable expenses = 18,000 × $6 = $108,000
Fixed expenses = $182,000
Expected net operating income = Total sales revenue – Variable expenses – Fixed expenses
= $360,000 – $108,000 – $182,000= $70,000
The expected percentage increase in net operating income = (Expected net operating income - Last year's net operating income) / Last year's net operating income*100= ($70,000 - $28,000) / $28,000*100= 150%
The expected total dollar net operating income for next year = $70,000
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7. A floor is covered by 800 tiles measuring 10 squared cm. How many square tiles of side 8 cm would be needed to cover the same floor?
Answer:
1000 tiles
Step-by-step explanation:
Determine total floor space
800 x 10 = 8000 squared cm total floor space.
Divide floor space by size of tile
8000 / 8 = 1000 tiles now required to cover the floor.
Dot plot 1 is the top plot. Dot plot 2 is the bottom plot.
According to the dot plots, which statement is true?
Х
The range of the data in dot plot 1 is less
than the range of the data in dot plot 2.
10
The mean of the data in dot plot 1 is
greater than the mean of the data in data
plot 2.
Х
х
The median of the data in dot plot 1 is
equal to the median of the data in dot plot
2.
The mode of the data in dot plot 1 is less
than the mode of the data in dot plot 2.
Answer:
the answer is b. The mode of the data in dot plot 1 is less than the mode of the data in dot plot 2.
Step-by-step explanation:
In the dot plots 1 and 2, the statement which is true is that the mean of the data in dot plot 1 is greater than the mean of the data in data plot 2.
What is dot plot?The dot plot is the way oif representation of the data. This data is plooted in the form of points or dots over an x-y axis. The dot polt is also known as the strip plot.
Dot plot 1 is the top plot. The value of it are as,
2,3,4,5,5,6,6,6,6,7,7,7,8,8,9,10
Dot plot 2 is the bottom plot. The value of it are as,
1,2,2,3,3,4,4,4,5,5,5,6,6,7,8,9
The options given in the problem are,
The range of the data in dot plot 1 is less than the range of the data in dot plot 2-Range is difference between the highest and lowest value. The range of the first dot plot is,
\(r_1=10-2=8\)
The range of the Second dot plot is,
\(r_2=9-1=8\)
Range of dot plots are equal.
The mean of the data in dot plot 1 is greater than the mean of the data in data plot 2.Mean of the dot plot one is 6.1875 and mean of the dot plot second is 4.625.
The median of the data in dot plot 1 is equal to the median of the data in dot plotThe median of the data in dot plot 1 is 6 and the median of the data in dot plot is 4.5. Thus they are not equal.
The mode of the data in dot plot 1 is less than the mode of the data in dot plot 2.The mode of the data in dot plot 1 is 6 and the mode of the data in dot plot 2 is 4 and 5. Thus this is not correct option.
Hence, in the dot plots 1 and 2, the statement which is true is that the mean of the data in dot plot 1 is greater than the mean of the data in data plot 2.
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Can y’all help me on question 4?!
Answer:
D
Step-by-step explanation:
Frank is at point G: (-6,-1)
Jimmy is at point B: (4,1)
What is the area (in square feet) of a rectangle that measures 12'-7" by 9'-9"?
Answer:
122.6875 (122 ft 8.25 in)
Step-by-step explanation:
12 ft 7in = 151 in
9 ft 9 in = 117 in
151 x 117 = 17667
17667in = 122 ft and 8.25 in = 122.6875 ft
If my answer is incorrect, pls correct me!
If you like my answer and explanation, mark me as brainliest!
-Chetan K
can you please help me I’ll pay you £100
Answer:
The new points to the triangle will be:
\(A(-6, 6)\\B(-6, 3)\\C(-8, 3)\)
Step-by-step explanation:
Because the reflection point is at \(x = -1\), all x values will subtract their distances from \(x = -1\) to get their new values. The y values remain the same.
The starting values are:
\(A(4,6)\\B(4,3)\\C(6,3)\)
Point \(A\) is 5 units away from \(x = -1\), so we'll subtract 5 from -1 to get the new x value: \(-1 - 5 = -6\), so \(A(-6, 6)\).
Point \(B\) is also 5 unit away from \(x = -1\), so we'll subtract 5 from -1 to get the new x value: \(-1 - 5 = -6\), so \(B(-6, 3)\).
Point \(C\) is 7 units away from \(x = -1\), so we'll subtract 7 from -1 to get the new x value: \(-1 - 7 = -8\), so \(C(-8, 3)\).
Answer:
No need to pay me, its my pleasure, also its not even in my country's currency so it would be worthless to me anyways.
5,4 and 4,4
Step-by-step explanation:
Using a calculator.. I need help please .
Answer:
Just input sin(9), sin(30), sin(81), etc.
For this set, you need a scientific calculator or else, you won't be able to answer that. There is a way but that is already obsolete now.
Which is the lowest rate? 8 cashiers for 96 people or 2 cashiers for 20 people
Find the lengths of the missing sides in the triangle. Write your answers as integers or as decimals rounded to the nearest tenth.
Answer:
The last one \((x=11.3, y=8)\).
Step-by-step explanation:
1) There are three trigonometric ratios for right-angled triangles.
\(sin()=\frac{opposite}{hypotenuse}\\cos()=\frac{adjacent}{hypotenuse}\\tan()=\frac{opposite}{adjacent}\)
In a right triangle, the hypotenuse, h, is the side opposite the right angle. Relative to the acute angle θ, check the attachment, the legs are called the opposite side, o, and the adjacent side a.
2) In this case, we are given a length and an angle to find x and y.
Let's find x first. To find x we need to use \(sin()=\frac{opposite}{hypotenuse}\).
\(sin(45)=\frac{8}{x}\\sin(45)x=8\\x=\frac{8}{sin(45)} \\x=11.31\)
Find y.
Notice that, we can use the Pythagorean Theorem \((c^2=a^2+b^2)\) to find y.
\(c^2=a^2+b^2\)
\(11.31^2=8^2+b^2\\11.31^2 - 8^2 = b^2\\63.9161 = b^2\\\sqrt{63.9161} = b\\b = 7.99\)
3) Round them off to the nearest tenth.
\(x=11.31\\x=11.3\)
\(y=7.99\\y=8\)
Therefore, the correct choice is the last one \((x=11.3, y=8)\).
Lamonte has 50 m of fencing to build a three-sided fence around a rectangular plot of land that sits on a riverbank. (The fourth side of the enclosure would be the river.) The area of the land is 288 square meters. List each set of possible dimensions (length and width) of the field.
The dimensions of the length and width are 25 meters and 12. 5 meters respectively.
How to determine the valuesArea of a rectangle
area of rectangle = l × w
where
l = length
w = width
Note that,
Perimeter = 2w+ l
50 = 2w + l
l = 50 - 2w
Hence,
area = w(50 - 2w)
288 = 50w - 2w²
-2w² + 50w - 288 = 0
-w² + 25w - 144 = 0
The dimension w can be found as follows;
w = - b / 2a
where
a = -1
b = 25
w = - 25 / 2 × -1
w = 12.5 meters
Then, we have that
l = 50 - 2w
Substitute the value of w
l = 50 - 2(12.5)
l = 50 - 25
I = 25 meters
Thus, the dimensions of the length and width are 25 meters and 12. 5 meters respectively.
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Kathryn and Pranav each improved their yards by planting grass sod and geraniums. They bought their supplies from the same store. Kathryn spent $27 on 6 ft^2 of grass sod and 5 geraniums. Pranav spent $51 on 9 ft of grass sod and 11 geraniums. What is the cost of one ft^2 of grass sod and the cost of one geranium?
Step-by-step explanation:
6ft² of grass sod + 5 geraniums = $27
9 ft² of grass sod + 11 geraniums = $51
Let x represent 1ft² of grass sod.
Let y represent 1 geranium.
We have 6x + 5y = $27.
=> 1.5(6x + 5y) = 1.5 * $27, 9x + 7.5y = $40.5.
9x + 11y = $51
- (9x + 7.5y = $40.5)
=> 3.5y = $10.5, y = $3.
Therefore 6x + 5($3) = $27,
6x + $15 = $27, 6x = $12, x = $2.
Hence 1ft² of grass sod costs $2
and 1 geranium costs $3.
Which situation has a net result of zero?
The temperature was -9'F and fell 9°F.
Janet had $4 and gave $3 to her friend.
High tide was 5.5 ft and now low tide is -0.5 ft.
The hot-air balloon rose 539 feet. It then lost 539 feet of altitude.
Answer:
D. The hot-air balloon... results in a net of zero
Step-by-step explanation:
Thanks for the points my guy :)
have a great day
Answer:
canberry
Step-by-step explanation:
Hi can any one teach me this constant difference
The constant differences between the consecutive terms are 2 (a); 2 (b), -3 (c), 7 (d), 1(e), and 6(f).
How do you find the constant difference in a sequence of numbers?In math, the constant difference can be defined as the number that defines the pattern of a sequence of numbers. This means that number that should be added or subtracted to continue with the sequence.
Due to this, to determine the constant difference it is important to observe the pattern and find out the number that should be added. For example, if the sequence is 2, 4, 6, 8, there is a difference of 2 between each of the numbers and this is the constant difference.
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A board is 6 1/2 feet long. You cut off a 1 3/4-foot piece and a 2 2/3 foot piece. How much of the original board is left?
Step-by-step explanation:
The feet long that the board is
\( = 6 \frac{1}{2} \\ \)
The piece of board cut off
\( = 1 \frac{3}{4} + 2 \frac{2}{3} \\ \)
\( = \frac{1 \times 4 + 3}{4} + \frac{2 \times 3 + 2}{3} \\ \)
\( = \frac{7}{4} + \frac{8}{3} \\ \)
\( = \frac{7}{4} \times \frac{3}{3} + \frac{8}{3} \times \frac{4}{4} \\ \)
\( = \frac{21}{12} + \frac{32}{12} \\ \)
\( = \frac{53}{12} \\ \)
The original board left
\( = 6 \frac{1}{2} - \frac{53}{12} \\ \)
\( = \frac{13}{2} - \frac{53}{12} \\ \)
\(= \frac{13}{2} \times \frac{6}{6} - \frac{53}{12} \times \frac{1}{1} \\ \)
\( = \frac{78 - 53}{12} \\ \)
\( = \frac{25}{12} \\ \)
\( = 2 \frac{1}{12} \\ \)
hope it helped !!!
kim and jake are competing in the big race. Jake starts at the starting line and rides at 2 meters per second. Kim gets a 6 meter head start and rides at 3 meters every 2 seconds. write an equation for kim and jake (hurry please)
1. An equation for Kim's time (in seconds) to complete the race is, t = x/2.
2. An equation for Jake's time (in seconds) to complete the race is, t = (x - 6)/1.5.
What is an equation?An equation is a mathematical statement (written with numbers, variables, and the equation sign) claiming that two mathematical expressions share value equality.
Equations are depicted using the equation sign (=).
The solution of the equation establishes the validity of the claim.
Kim's running speed = 2 meters per second
Jake's running speed = 1.5 meters per second (or 3 meters per 2 seconds)
Let the total distance for the race = x and the total time taken by either Kim or Jakes = t.
Time = Distance/Speed
Kim's equation for time is t = x/2.
Jake's equation for time is t = (x - 6)/1.5.
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Can I find a tutor to help me bro ?
Solution
Given the quadratic equation:
x² + 2x + 7 = 21
x² + 2x + 7 - 21 = 0
x² + 2x - 14 = 0
a = 1, b = 2, c = - 14
(1) The number of solutions of a given quadratic equation is determine by the discriminant.
From the given values;
(2)² - 4(1 x -14) = 4 + 56 = 60
60 > 0 ( 2 solutions)
1 positive solution and 1 negative solution
Thus, number of positive solutions to this equation is one
(2) The greatest solution or positive solution to the equation is calculated as;
There are 48 students in an elementary statistics class. On the basis of years of experience, the instructor knows that the time needed to grade a randomly chosen first examination paper is a random variable with an expected value of 5 min and a standard deviation of 4 min. (Round your answers to four decimal places.)
(a) If grading times are independent and the instructor begins grading at 6:50 P.M. and grades continuously, what is the (approximate) probability that he is through grading before the 11:00 P.M. TV news begins?(b) What is the (approximate) probability that the sample mean hardness for a random sample of 39 pins is at least 51?
Answer:
a) 64.06% probability that he is through grading before the 11:00 P.M. TV news begins.
b) The hardness distribution is not given. But you would have to find s when n = 39, then the probability would be 1 subtracted by the pvalue of Z when X = 51.
Step-by-step explanation:
To solve this question, we need to understand the normal probability distribution and the central limit theorem.
Normal probability distribution
When the distribution is normal, we use the z-score formula.
In a set with mean \(\mu\) and standard deviation \(\sigma\), the zscore of a measure X is given by:
\(Z = \frac{X - \mu}{\sigma}\)
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.
Central Limit Theorem
The Central Limit Theorem estabilishes that, for a normally distributed random variable X, with mean \(\mu\) and standard deviation \(\sigma\), the sampling distribution of the sample means with size n can be approximated to a normal distribution with mean \(\mu\) and standard deviation \(s = \frac{\sigma}{\sqrt{n}}\).
For a skewed variable, the Central Limit Theorem can also be applied, as long as n is at least 30.
For the sum of n trials, the mean is \(\mu*n\) and the standard deviation is \(s = \sigma\sqrt{n}\)
In this question:
\(n = 48, \mu = 48*5 = 240, s = 4\sqrt{48} = 27.71\)
These values are in minutes.
(a) If grading times are independent and the instructor begins grading at 6:50 P.M. and grades continuously, what is the (approximate) probability that he is through grading before the 11:00 P.M. TV news begins?
From 6:50 PM to 11 PM there are 4 hours and 10 minutes, so 4*60 + 10 = 250 minutes. This probability is the pvalue of Z when X = 250. So
\(Z = \frac{X - \mu}{\sigma}\)
By the Central Limit Theorem
\(Z = \frac{X - \mu}{s}\)
\(Z = \frac{250 - 240}{27.71}\)
\(Z = 0.36\)
\(Z = 0.36\) has a pvalue of 0.6406
64.06% probability that he is through grading before the 11:00 P.M. TV news begins.
(b) What is the (approximate) probability that the sample mean hardness for a random sample of 39 pins is at least 51?
The hardness distribution is not given. But you would have to find s when n = 39(using the standard deviation of the population divided by the square root of 39, since it is not a sum here), then the probability would be 1 subtracted by the pvalue of Z when X = 51.