Cars enter a car wash at a mean rate of 4 cars per half an hour. What is the probability that, in any hour, exactly 4 cars will enter the car wash? Round your answer to four decimal places.

Answers

Answer 1

The probability that exactly 4 cars will enter the car wash in an hour is 0.195

What is the probability that, in any hour, exactly 4 cars will enter the car wash?

Generally, This is a Poisson process, where the mean number of cars entering the car wash is 4 cars per hour. The probability of exactly 4 cars entering in an hour is given by the Poisson probability mass function:

P(X = 4) = (e^(-4) * 4^4) / 4!

where e is approximately 2.71828, and 4! is

4 * 3 * 2 * 1 = 24.

Plugging in the values, we get:

P(X = 4) = (2.71828^(-4) * 4^4) / 24

P(X = 4) =0.195

Read more about probability

https://brainly.com/question/30034780

#SPJ1


Related Questions

A storm that moved through several states at a speed of 60 miles per hour affected 219 miles of land. What did that make the storm

Answers

The longest tornado ever recorded spanned 219 miles of land as it swept through many states at a pace of 60 miles per hour.

What are the importance of vector calculus?A tornado could cause a natural disaster to wreak havoc in significant geographic areas.A violent column of air between a thunderstorm and the earth is what is known as a tornado.In severe tornadoes, winds exceeding 200 miles per hour (h) are not uncommon.In conclusion, the longest tornado ever recorded affected 219 miles of land as it swept through many states at a speed of 60 miles per hour.Mathematically, a tornado is vector calculus with a fury. Severe storms are the result of the interaction of the two scalar forces of pressure and humidity with the vector field known as wind.

To learn more about tornado, refer to:

https://brainly.com/question/29099905

#SPJ4

What is the probability that a randomly selected box of the cereal contains less than 9.65 ounces of cereal

Answers

There is a 0.0001 percent chance that the average amount of cereal in these boxes is less than 9.65 ounces.

What is meant by probability?The likelihood of an event happening is gauged by probability. Many things are impossible to completely predict in advance. We can only forecast how likely an event is to occur using it, or how likely it is to occur.The probability is a metric for determining how likely an event is to occur. It gauges the event's degree of certainty. The probability formula is presented as follows: P(E) = Number of Favorable Outcomes/Number of Total Outcomes.By dividing the number of preferable possibilities by the total number of potential outcomes, probability, which measures the likelihood that an event will occur, is obtained.

Given that,

Mean µ = 9.70

Sample size = n = 5

standard deviation = σ = 0.03

Its distribution is normal, therefore

σx = σ/

σx = 0.03

σx = 0.0134

We must now determine the z value in order to use the table.

z = (x - µ) ÷ σ

z = (9.65 - 9,70) ÷ 0.0134

z = -3.73

Now

From the probability index tables

So P (z ≤ - 3.73) = 0.0001

Hence, the correct option is e) 0.0001

The complete question is:

A company’s cereal boxes advertise that each box contains 9.65 ounces of cereal. In fact, the amount of cereal in a randomly selected box follows a Normal distribution with mean μ = 9.70 ounces and standard deviation σ = 0.03 ounce. Now take an SRS of 5 boxes. What is the probability that the mean amount of cereal in these boxes is less than 9.65 ounces?

a. 0.4525

b. 0.9522

c. 0.9999

d. 0.0478

e. 0.0001

To learn more about probability, refer to:

https://brainly.com/question/24756209

#SPJ4

Can you help me with this

Answers

slope formula =y2-y1/x2-x1

3 -(-9) =12
6-(8) =-2
12/-2=

the slope = -6/1

Alana and Petra go to a ued book ale , where every book i the ame price. Alana buy 4 book and Petra buy 2 book. They run into their friend angu, who really love to read, and dicover that he ha bought 16 book. Angu received a $15 dicount, but he till pent $5 more than Alana and Petra combined. How much doe one book cot?

Answers

A book cost $2.00.

What are variables in maths?

In Maths, a variable is an alphabet or term that represents an unknown number or unknown value or unknown quantity. The variables are specially used in the case of algebraic expression or algebra. For example, x+9=4 is a linear equation where x is a variable, where 9 and 4 are constants.

What are the 2 basic types of variables?

Variables may be classified into two main categories: categorical and numeric. Each category is then classified in two subcategories: nominal or ordinal for categorical variables, discrete or continuous for numeric variables.

Given the no of books purchased by

Alana =4

Petra =2

Angus = 16

So, the total price of 4 books of Alana =$4

Total price for Petra = $2

Total price of Alana and Petra =4x+2x

=6x

Total price for Angus = 16x

But given Angus received a discount  of $15

So price post discount = 16x- 15

According to the question

16x-15 = 6x +5

Adding 15 both sides

16x +15-15 = 6x + 5+15

16x= 6x+20

Subtracting 6x both sides

16x - 6x = 6x - 6x + 20

10x = 20

i.e x=2

Cost of one book = $2

To learn more about variables visit:

https://brainly.com/question/17344045

#SPJ4

ES = ___ units

Round your answer to the nearest tenth.

Answers

Answer:

15

Step-by-step explanation:

What’s the formula to find principal please tell me please

Answers

Answer:

Step-by-step explanation:

(100xInterest)(RatexTime)

hope this helps

Step-by-step explanation:

The formula for calculating Principal amount would be P = 100I / (RT) where Interest is Interest Amount, R is Rate of Interest and T is Time Period.

Solve for x: -24 = 6x

Answers

Answer:

x = -4

Step-by-step explanation:

Solve for x: -24 = 6x

-24 = 6x

x = -24 : 6

x = -4

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

check

-24 = 6(-4)

-24 = -24

the answer is good

Mario has 3/4 cups of chocolate chips needs 1/3 cup to make a batch of cookies how many batches can Mario make if he uses all of his chocolate chips

Answers

In the given equation, Mario can make 2.25 batches of cookies using all of his chocolate chips.

How to find the given equation?

First, you can find out how many total cups of chocolate chips Mario has by multiplying the number of cups per unit (3/4) by the number of units (1).

[tex]3/4 cups * 1 = 3/4 cups\\[/tex]

Then you can divide the total amount of chocolate chips Mario has by the amount of chocolate chips needed per batch:

[tex]3/4 cups / 1/3 cup/batch = 3/4 cups * 3/1 cup/batch = 9/4 cups/batch[/tex]

Finally, you can convert this to a whole number by dividing both the numerator and denominator by their greatest common factor, which is 1:

[tex]9/4 cups/batch = (9/1) / (4/1) = 9/4 = 2.25 batches[/tex]

Mario can make 2.25 batches of cookies using all of his chocolate chips.

To know more about numerator and denominator  visit: https://brainly.com/question/7067665

#SPJ4

Tyrese works each day and earns more money per hour the longer he works. Write a function to represent a starting pay of $20 with an increase each hour by 3%. Determine the range of the amount Tyrese makes each hour if he can only work a total of 8 hours.

Answers

The range of the amount Tyrese makes each hour if he can only work a total of 8 hours is 20 ≤ x ≤ 24.80

What is a range?

The range is the space between the highest and lowest numbers.

Given: Tyrese works every day and gets paid more per hour the more time he puts in. Create a function to represent a starting wage of $20 that rises by 3% each hour.

To find: Establish the range of Tyrese's hourly pay if he can only work a total of 8 hours.

The beginning wage is $20.

Suppose x hours are in a day.

A $20 salary is offered, with a 3% hourly raise.

e.g., increment = (3/100)*20*x = (3/5)x

A function's maximum possible earnings are

y = 20 + (3/5)x

He is only allowed to work a total of 8 hours, per our instructions.

Therefore, the most money she can make in 8 hours is

y = 20 + (3/5)*8

y = 20 + 4.8

y = 24*8

$20 is the first sum.

As a result, if Tyrese can only work a total of 8 hours every day, the range of his hourly wage is .

Therefore, the correct answer is option B) 20 ≤ x ≤ 24.80.

To learn more about range refer to:

brainly.com/question/2264373

#SPJ4

Your friend has read 6 more than twice as many pages as your
sister has read. Let 4
be the number of pages that your sister has
read. Write an expression for the number of pages that your friend
has read

Answers

Answer:

Expression: 2s + 6

# of Pages Friend Read: 14 pages

Step-by-step explanation:

Let's call the number of pages your sister has read, s, and the number of pages your friend has read, f. We will make our equation first. If your friend has read 6 more than twice as many pages as your sister has, your equation would look like this:

f = 2s + 6

That is your equation for how many pages your friend read, your expression would be just 2s + 6. Now, we will substitute in 4 for s, and we get:

f = 2 * 4 + 6

Multiplying gives:

f = 8 + 6 = 14

So your friend has read 14 pages.

Hope this helped!

How do you find the slope of two points on a graph?

Answers

To find the slope of two points on a graph, use the formula:

[tex]Slope =\frac{y2 - y1}{x2 - x1}[/tex]

Substitute the coordinates of the two points into the formula and solve for the slope.

Finding the Slope of Two Points on a Graph

The slope of two points on a graph is a measure of how steep the line connecting the two points is. To find the slope, you can use the slope formula: [tex]Slope =\frac{y2 - y1}{x2 - x1}[/tex]

This formula requires the coordinates of the two points, which can be found on the graph. Once you have the coordinates, you can substitute them into the formula and solve for the slope. This will give you the slope of the line connecting the two points.

Learn more about slope of a line: https://brainly.com/question/16949303

#SPJ4

Explain how the quotient was determined.

Answers

Because it started with one at the end and the other numbers didn’t matter because of that because the eight was small so you are multiplying by one but anything by one will always be one

what value of x would prove that the following triangle is a right angle? Answers x=7 x=2 x= 14 x= 10​

Answers

Step-by-step explanation:

Pythagoras' Theorem

For Pythagoras' Theorem to be valid, the triangle must be a right-angled one.

The formula is:

c^2 = a^2 + b^2

Where c is the longest side. While a,b are the side lengths.

Solution

Using the above formula and the measurements given in the question, we can find the value of x.

By Pythagoras' Theorem,

26^2 = (5x)^2 + (12x)^2

676 = 25x^2 + 144x^2

169x^2 = 676

x^2 = 676 ÷ 169

x^2 = 4

x = 2

The town librarian bought a combination of new-release movies on DVD for $20 and classic movies on DVD for $8. Let
x represent the number of new releases, and let y represent the number of classics. If the librarian had a budget of
$500 and wanteho purchase as many DVDs as possible, which values of x and y could represent the number of new
release and classie movies bought?
O x= 8, y = 45
O x= 10, y = 22
O x = 16. Y = 22
Ox= 18, y=18
Mark this and return
Save and Exit
Next
Submit​

Answers

The Correct answer is option (C) x = 16. Y = 22 . number of new-release movies on DVD is 16 and the number of classic movies on DVD is 22 .

What is linear equation?

An equation is said to be linear if the maximum power of the variable is consistently 1. Another name for it is a one-degree equation. A linear equation with one variable has the conventional form Ax + B = 0. In this case, the variables x and A are variables, while B is a constant. A linear equation with two variables has the conventional form Ax + By = C. Here, the variables x and y, the coefficients A and B, and the constant C are all present.

Given,

To find the values of X and Y,

Let x = number of new releases

Let y = number of classics.

The equation to solve the question is ,

20x + 8y = 500

When x= 16 and y = 22

= 20x + 8y

= 20(16) + 8(22)

= 320 + 176

= 496

Therefore, the number of new-release movies on DVD is 16 and the number of classic movies on DVD is  x= 16, y = 22

To learn more about Linear Equations visit:

brainly.com/question/2030026

#SPJ4

I want to know how to get the GCF and LCM of 8,24,48

Answers

Answer:

GCF = 8

LCM = 48

Step-by-step explanation:

convert 11.011 to a base 10 number​

Answers

Multiply each digit by its corresponding place value and add the results: 11 + 0.011

11.011 = 11 + 0.011 = 11.011

How to covert binary number to decimal number?

Once the bits of the binary number have been multiplied by the corresponding positional weights, the binary number can then be converted into its corresponding decimal number by adding the resulting products.

To convert a number in base 2 (binary), base 8 (octal) or base 16 (hexadecimal) to a base 10 (decimal) number, you can use the following method:

Write the number in base 2, 8, or 16 and the corresponding base 10 place values.

Multiply each digit by its corresponding place value and add the results.

For example, to convert the base 10 number 11.011 to a base 10 number:

Write the number and the corresponding base 10 place values: 11.011

Multiply each digit by its corresponding place value and add the results: 11 + 0.011

11.011 = 11 + 0.011 = 11.011

As the number is already in base 10, it does not need to be converted. The value is 11.011

To know more about decimal number visit:

https://brainly.com/question/4708407

#SPJ1

A large helium balloon is tethered to the ground by two taut lines. One line is 100 ft. Long and makes an 80 degree angle with the ground. The second line makes a 40 degree angle with the ground. How long is the second line?

Answers

The second line is 153ft long.

We are making a figure out of the given statment. Where we have the Triangle ABC and other two Triangle ADB and ADC inside Triangle ABC. Here Angle ADC = 80 degress and Angle ACD = 40 egress.

According to given statement and figure,

In triangle ABO, AD= 100 ft

Hence, BD/AD = Cos80

or, BD = (100 * Cos80)

or, BD = 17.36 ft

Now, AB/AD = Sin80

or, AB = (100* Sin 80)

or, AB = 98.48

Now, In case of triangle ABC

AB/AC = Sin40

or, AC = AB/ Sin 40

or, AC = 98.48/ Sin40

or, AC = 153.2 ft (nearly equal to 153 ft)

The second line is 153ft long.

To know more about Trigonometric solution here:

https://brainly.com/question/29088508#

#SPJ4

Which triangles are congruent by ASA?
ABC and TUV
VTU and ABC
VTU and HGF
none of the above

Answers

Still in need of help ??
the answers VTU and ABC

The ratio of the number of report cards Ms. Wickham folded to the number that Ms. Cho folded was 2:3. At the end of the day, Ms. Leiva and Mr. Gamory folded 300 report cards. Who folded more report cards and by how many

Answers

Ms. Wickham folded 200 report cards and Ms. Cho folded 300 report cards, giving Ms. Cho an average of 100 report cards.

Ms. Wickham and Ms. Cho together folded 500 report cards.

Ms. Wickham folded 200 report cards

(200/500 = 2/5)

Ms. Cho folded 300 report cards

(300/500 = 3/5)

Mr. Leiva and Mr. Gamory folded 300 report cards.

Ms. Cho folded more report cards than Ms. Wickham, by

100 (300 - 200 = 100).

Ms. Wickham and Ms. Cho together folded 500 report cards, with the ratio of Ms. Wickham's report cards to Ms. Cho's being 2:3. Ms. Wickham folded 200 report cards, while Ms. Cho folded 300. At the end of the day, Mr. Leiva and Mr. Gamory folded an average 300 report cards. This meant that Ms. Cho folded more report cards than Ms. Wickham, by 100. Therefore, Ms. Cho folded 400 report cards in total, while Ms. Wickham only folded 300.

Learn more about average here

https://brainly.com/question/24057012

#SPJ4

Dalis' employer pays $2,150 in health insurance and $86
in life insurance per year. She also gets $3,520 in paid time
off per year. Her monthly gross pay is $4,370. What are
Dalis' total job benefits?

Answers

Answer: chiki

Step-by-step explanation:

Shade the points in the plane whose x-coordinates are greater than their y-coordinates. Write the inequality that describes these points.

Answers

The inequality that describes these points is y ≤ -1/2(x) -3. The graph is given the attachment.

How to graph an inequality?

To graph a linear inequality in two variables (say, x and y), start with y on one side. Consider the related equation obtained by changing the inequality sign to an equality sign. This equation's graph is a straight line.

If the inequality is strict (< or >), draw a dashed line. If the inequality is not strict (≤ or ≥), draw a solid line.

Finally, choose one point that is not on either line ((0,0) is usually the easiest) and determine whether these coordinates satisfy the inequality or not. If they do, shade the half-plane containing that point. If they don't, shade the other half-plane.

Graph each of the system's inequalities in a similar way.

Learn more about inequality

https://brainly.com/question/30231190

#SPJ1

How many times and how many ounces should I feed my goat if it is 7 pounds and I feed it 3 times a day

Answers

Since you're feeding it three times a day, you should feed your goat 0.74 ounces per feeding.

What is feeding?

The act of feeding involves giving a baby a mother's breast milk, either directly from the breast or by expressing (pump-out) the milk from the breast and giving it to the baby in a bottle.

Define Ounces and Pounding.

In the traditional method of measurement, a pound is used to measure weight. In the conventional system, ounces are smaller weight units that are defined in terms of pounds. 1 pound Equals 16 ounces.

Goats typically need around 2% to 4% of their body weight in feed per day. If your goat weighs 7 pounds, and you want to feed it 2% of its body weight per day, you would need to feed it 0.14 pounds of food per day, or 2.24 ounces per day. Since you're feeding it three times a day, you should feed it 0.74 ounces per feeding.

To learn more about Ounce visit:

https://brainly.com/question/29374025

#SPJ1

simply the following
a) 2(y-1)/3-3(y-2)/4=1
b) 3x=44/5=2x+6

Answers

The simplified value of x is 44 / 15 or 7 / 5 and value of y is -2

What is simplification?

Simply or simplification is reducing the expression/fraction/problem in a simpler form. It makes the problem easy with calculations and solving.

Given that, simply the following

a) 2(y-1)/3-3(y-2)/4=1

b) 3x=44/5=2x+6

1) 2(y-1) / 3 - 3(y-2) / 4 = 1

Multiplying by 12 to both sides,

8(y-1) - 9(y-2) = 12

8y-8 - 9y+18 = 12

-y + 10 = 12

y = -2

2) 3x = 44 / 5 = 2x+6

3x = 44 / 5

Multiplying by 5 to both sides,

15x = 44

x = 44 / 15

or,

44 / 5 = 2x + 6

Multiplying by 5 to both sides,

44 = 10x + 30

14 = 10x

x = 7 / 5

Hence, the simplified value of x is 44 / 15 or 7 / 5 and value of y is -2

For more references on simplification, click;

https://brainly.com/question/2804192

#SPJ1

The total number of books sold from 2010-2015 from
Amazon can be modeled by the function
3
2
f(x) = 40x + 8x + 14824x + 33000and the number of kinds
of books at Amazon from that same time period can be modeled
as g(x): =
10x + 22, where x is the number of years since
2010. What is the average number of each kind of book
Amazon sold?

Answers

Answer:

If you want to find out how many print copies the book is selling, just click the Paperback or Hardcover edition of the book on Amazon, scroll down to Product Details on that page, and find the Amazon Best Sellers Rank for the print edition.

Step-by-step explanation:

15. A pool can hold 850 gallons. It now has 598 gallons of
water and is being filled at the rate shown. How many
more minutes, m, can water continue to flow into the
pool before it overflows? Write and solve an inequality.
Then graph the solutions.

Answers

850 >= 598+15.75m
252 >= 15.75m
16>=m
The pool can be filled for 16 minutes before it overflows

What it means when a function and its inverse is the same?

Answers

Step-by-step explanation:

it means that the graph of the function above y=x must be the mirrored image of the graph under y=x.

it means that the function applied to itself gives x.

f(f(x)) = x

e.g.

f(x) = 5 - x

f(f(x)) = 5 - (5 - x) = 5 - 5 + x = x

so, this f(x) is its own inverse.

A company has two manufacturing plants with daily production levels of 5x +14 items and 3x - 5 items, respectively. The first plant produces how many more items daily than the second​ plant?

Answers

Answer:

21x

Step-by-step explanation:

5x+14=19x

3x-5=-2x

-2x-19x=21x

I NEED HELP ASAP!!!!!!!!

Answers

Answer:

(- 1, 9 )

Step-by-step explanation:

6x - y = - 15 → (1)

x + 2y = 17 → (2)

multiplying (1) by 2 and adding to (2) will eliminate y

12x - 2y = - 30 → (3)

add (2) and (3) term by term to eliminate y

13x + 0 = - 13

13x = - 13 ( divide both sides by 13 )

x = - 1

substitute x = - 1 into either of the 2 equations and solve for y

substituting into (2)

- 1 + 2y = 17 ( add 1 to both sides )

2y = 18 ( divide both sides by 2 )

y = 9

solution is (- 1, 9 )

The table shows a bacterial population y after x days


days, X 0,1,2,3,4

Population,8,24,72,216,648


Write an exponential function that represents the population


Y=

Answers

The exponential function that represents the population is y = a*3^x.

What is exponential function?

The formula for exponential functions is y = ab^x, where b is the constant ratio and a  is the starting point. Observe that as the value of x increases by a constant amount, the value of y increases by a common ratio by looking at a table of ordered pairs. All exponential functions share this trait.

We have to find the exponential function for the given table.

Since,

Exponential function = ab^x

where,

a is the starting point

b is the common ratio.

Here,

Common ratio = 24/8 = 72/24 = 216/72 = 648/216 = 3

So, the function becomes,

Exponential function = y = a*3^x

Hence, the exponential function that represents the population is

y = a*3^x.

To know more about exponential function, click on the link

https://brainly.com/question/2456547

#SPJ4

How to graph 4x-6y=36

What’s the x intercept

What’s the y intercept

Answers

Therefore . the solution of the given problem of equation comes out to be x-intercept(s): (9,0) and y-intercept(s): (0,−6).

Clarify the equation

A depiction of two equal variables, one on either side of a "equals" sign, is what constitutes an equation in mathematics. To solve common issues, one can use equations. We frequently look for help with pre algebra to overcome obstacles in real life. Basic mathematical concepts are covered in pre-algebra lessons.

Here,

the x-intercepts,

In order to determine the x-intercept(s), put in for y and calculate 4x6y=36.

Make the equation work.

x=9 point form x-intercepts.

x-intercept(s): \s(9,0) (9,0)

the y-intercepts, please.

In order to determine the y-intercept(s), replace with and solve for y=.4(0-)6y=36.

Make the equation work.

To continue, tap.

Point shape y=6 y-intercept(s).

The y-intercept is (0, 6).

Write down the junctions.

x-intercept(s): (9,0)

The y-intercept is (0, 6).

Therefore . the solution of the given problem of equation comes out to be x-intercept(s): (9,0) and y-intercept(s): (0,−6).

To know more about equation visit:

brainly.com/question/649785

#SPJ1

Other Questions
Cystic fibrosis is a recessively inherited disorder that results from a mutation in the gene encoding CFTR chloride ion channels located on the surface of many epithelial cells. As shown in the figure, the mutation prevents the normal movement of chloride ions from the cytosol of the cell to the extracellular fluid. As a consequence of the mutation, the mucus layer that is normally present on the surface of the cells becomes exceptionally dehydrated and viscous.An answer to which of the following questions would provide the most information about the association between the CFTR mutation and the viscous mucus?answer choicesIs the mucus also secreted from the cells through the CFTR proteins?How does the disrupted chloride movement affect the movement of sodium ions and water by the cell?How does the mutation alter the structure of the CFTR proteins?What is the change in nucleotide sequence that results in the CFTR mutation? television journalist barbara walters died on december 30. what was her first job in broadcasting? If an amount of heat Q is needed to increase the temperature of a solid metal sphere of diameter D from 4C to 7C, the amount of heat needed to increase the temperature of a solid sphere of diameter 2D of the same metal from 4C to 7C is A. 8Q B. 40 C. 20 D. Q What are the 3 economics systems? What is the value of 3 in tan? The length of the base of an isosceles triangle is x. The length of a leg is 5x -2. The perimeter of the triangle is 106. Find x. X = In at least two hundred word,discuss why " Dsires Baby" is or is not relevant today What is the measure of A if it is complementary to B that has a measure of 55? 1.6-A Describe how ONE state in Europe developed, 1200-1450 express 832 in the form 4n where n is the integral Across a resistor, voltagea. dropsb. buildsc. speeds up I really need help on this asap The Declaration of Independence And the articles below are similar because both _____. * 4 points Captionless Image describes powers of the government describe the structure of the government are enforced in every country in the world describe personal freedoms to which every person is entitled 1. When conducting a test on what kind of music increases the growth of plants, all of the following would fail to meet to fair test standard EXCEPT (1 point) using different kinds of plants. giving some plants more water than others. exposing the plants to different types of music. using nutrient-rich soil for one and lesser soil for others. 2. Engineering uses scientific thinking to solve real-world problems. (1 point) True False 3. What does it mean to test a hypothesis? (1 point) Pass a quiz on other scientists results Analyze only the results from scientific sources Not make assumptions about how an experiment will turn out See if the results of an experiment are what the scientist predicted The solution set of 12 x squared minus 14 x equals 10 is A=[2 3) B=(1 2) find AB [0 8) (2 -1) How do you give value to your own culture? Which was the only nation-state which had colonies on five different continents at the outbreak of WWI in 1914 Just say no- How does paragraph 4 contribute to the development of ideas in the text A high school statistics class wants to conduct a survey to determine what percentage of students in the school would be willing to pay a fee for participating in after-school activities. Twenty students are randomly selected from each of the freshman, sophomore, junior, and senior classes to complete the survey. This plan is an example of which type of sampling