Exercise 3.29. In a school there are four kindergarten classes, with 21, 24, 17 and 28 students. We choose one of the 90 kindergarten students randomly, and denote the number of students in her class by X. Find the expectation and variance of X.

Answers

Answer 1

Answer:

Expected mean = 23.2159

Variance = 15.89

Step-by-step explanation:

Given that :

Number of kindergarten students (X) :

21 + 24 + 17 + 28 = 90

P(X):

21/ 90 = 0.233

24/90 = 0.2667

17/90 = 0.1889

28/90 = 0.3111

X : ____ 21 ____24 _____ 17 ______ 28

P(x) : _ 0.233 _ 0.2667 __ 0.1889 __ 0.3111

E(X) = Σ[(p)*p(x)]

(21 * 0.233) + (24 * 0.2667) + (17 * 0.1889) + (28 * 0.3111) = 23.2159

Var(X) : Σ(x²*p(x)) - E(x)²

x² * p(x) = (21^2 * 0.233) + (24^2 * 0.2667) + (17^2 * 0.1889) + (28^2 * 0.3111) - 23.2159^2

554.8667 - 538.97801281

= 15.88868719

= 15.89


Related Questions

At the local sandwich shop, employees earn double time for any hours worked in addition to their regular 39-hour
week. Last week, Cooper Jones worked his regular 39 hours plus 9 hours of overtime. Cooper is paid $23.90 per
hour. What is his total pay for the week?

Answers

Answer:

8,030.4

Step-by-step explanation:

Answer:

$287.04

Step-by-step explanation:

add 39 and 9 multiply the sum by $23.90 and then multiply by two and boom, $287.04

Solve the equation. 2 + |t+ 6| = 12

Answers

Answer:

t = 4 or t = -16

Step-by-step explanation:

Let's solve your equation step-by-step.

2+|t+6|=12

|t+6|+2=12

Step 1: Add -2 to both sides.

|t+6|+2+−2=12+−2

|t+6|=10

Step 2: Solve Absolute Value.

|t+6|=10

We know eithert+6=10 or t+6=−10

t+6=10(Possibility 1)

t+6−6=10−6(Subtract 6 from both sides)

t=4

t+6=−10(Possibility 2)

t+6−6=−10−6(Subtract 6 from both sides)

t=−16

What is the solution to the system of equations graphed below

(2,-3)
(-3,2)
(-2,3)
(3,-2)

Answers

The answer will be (2,-3) it’s 2 to the right and 3 down.

Answer: The answer will be (2,-3) it’s 2 to the right and 3 down.

Step-by-step explanation: yay

Mr. Pharm put $1,550 into a savings account. The account pays 3.5% simple interest on an annual basis. If he does not add or withdraw money from the account, how much interest will he earn after 2 years?

Answers

Answer:

Mr. Pharm will earn $108.50 in two years, having deposited $1,500 into an account earning 3.5% simple interest.

Step-by-step explanation:

1550 * 3.5% * 2 = $108.50


Identify the two missing sides of the 45-45-90 triangle

Answers

x= 8

y= 8root2




........................



A square has a side length 9cm. What is its area in square centimeters? A square has a side length 9cm2. What is its area in square centimeters?

Answers

Answer:

Step-by-step explanation:

A.

Given parameter:

  Side length  = 9cm

Unknown;

Area of the square  = ?

Solution:

The shape given is a square.

 Area of a square  = L²

 L is the side length

  Insert the parameters and solve;

     Area of the square  = 9²  = 81cm²

B.

Given parameters:

Area of the square = 9cm²

Unknown:

Side length  = ?

Solution:

The shape is a square;

  Area of a square  = L²

         9  = L²

          L = √9 = 3cm

what is the equation of a line thag has a slope of -5 and a y-intercept of -7?
fill in the blanks: y=____x+____​

Answers

Answer:

y= -5x + -7 is your answer

What is the solution to this linear equation?
4b + 6 = 2 - b + 4

Answers

b = 0

To solve make b the subject so:

4b + 6 = 2 - b + 4

5b + 6 = 6

5b = 0

5 = 0/5

= 0

Gabby accumulated $12,000 in credit card debt. If the interest rate is 4% per year and she does not make any payments for 8 years, how much will she owe on this debt in 8 years by compounding continuously?

Answers

Answer:

$16,525.53.

Step-by-step explanation:

A=Pe^rt

P=$12,000

r=0.04

t=8 years

Assume that 25% of all households in Santa Clara county have a burglar alarm (population characteristic). A random sample of 200 Santa Clara county households is taken. What is the probability that between 20% (0.2) to 30% (0.3) of the households in the sample have a burglar alarm

Answers

Answer:

The probability is  [tex]P( 0.2 < p < 0.3) = 0.89751[/tex]

Step-by-step explanation:

From the question  we are told that

   The population proportion is  p =  0.25

   The sample size is  n  =  200  

     

Generally given that the sample size is large the mean of this sampling distribution is mathematically represented as [tex]\mu_{x} = p = 0.25[/tex]

 Generally the standard deviation is mathematically represented as

        [tex]\sigma = \sqrt{ \frac{ p (1- p ) }{n} }[/tex]

=>     [tex]\sigma = \sqrt{ \frac{ 0.25(1- 0.25 ) }{200} }[/tex]

=>     [tex]\sigma = 0.03062[/tex]

Generally the probability that between 20% (0.2) to 30% (0.3) of the households in the sample have a burglar alarm is mathematically represented as  

      [tex]P( 0.2 < p < 0.3) = P(\frac{ 0.2 - 0.25}{ 0.03062 } < \frac{p- \mu_{x}}{\sigma } < \frac{ 0.2 - 0.25}{ 0.03062 } )[/tex]

[tex]\frac{p -\mu}{\sigma }  =  Z (The  \ standardized \  value\  of  \  p )[/tex]

=>   [tex]P( 0.2 < p < 0.3) = P(-1.6329 < Z <1.6329 )[/tex]

=>   [tex]P( 0.2 < p < 0.3) = P( Z< 1.6329) - P( Z <- 1.6329 )[/tex]

From the z table  the area under the normal curve to the left corresponding to  1.6329 and  -1.6329  is

    [tex]P( Z< 1.6329) = 0.94875[/tex]

and

    [tex]P( Z <- 1.6329 ) = 0.051245[/tex]

So

   [tex]P( 0.2 < p < 0.3) = 0.94875 - 0.051245[/tex]

=> [tex]P( 0.2 < p < 0.3) = 0.89751[/tex]

Suppose commute times in a large city are normally distributed and that 63.70% of commuters in this city take more than 22 minutes to commute one-way. If the standard deviation of such commutes is 6.3 minutes, what is the mean commute?

Answers

Answer:

The mean is 24.205

Step-by-step explanation:

Firstly, we need to get the z-score

From the question, the probability we have is the probability that commuters take more than 22 minutes to commute one-way

So the probability we had was;

P( x > 22)

So we need the z-score corresponding to 63.70% or simply 0.637

We can use the standard normal distribution table to get this

Mathematically, from the standard normal distribution table this is -0.35

z-score = (x- mean)/SD

-0.35 = (22-mean)/6.3

22-mean = -2.205

mean = 22 + 2.205 = 24.205

Question 8 (2 points)
15 is 25% of
Brank 1:
HELPPP MEEE

Answers

Answer:

15 is 25% of 60

Step-by-step explanation:

15 x 4 = 60

25% x 4 = 100%

Answer:

I think that might be 60

Step-by-step explanation:

1/3-5/15-2/8+1/6=
(2/5-4/3):(5/4-2/6)+9/12)=

Answers

Answer:

is 13 giv brainliest PLSSSSSSSSSSSSSSSSSSSSSSSSSSSSS

Step-by-step explanation:

how many grams in 1.7x 10^7 ug

Answers

Answer:

17 grams

Step-by-step explanation:

Solve. Explain your answers in the box below.

a. Travis estimated the product of 602 and 341 to be 1,800. His work is shown below. Find and explain Travis's error.



600×300
6 hundreds × 3 hundreds =18 hundreds

600×300=1,800


b. Margaret said the exact product of 602 and 341 is 205,282. Is she correct? Use paper and the standard algorithm to support your reasoning.

Answers

Answer:

Travis estimated the product of 602 and 341 to be 1,800. His work is shown below. Find and explain Travis's error. 600×300 6 hundreds × 3 hundreds =18 hundreds 600×300=1,800 b. Margaret said the exact product of 602

Step-by-step explanation:

i hoped it was right!

Which is the slope of the line that passes through the points (-2, 4) and
(5, -1)?

Answers

The reason I plugged 4 into the y spot of the equation and -2 into the x spot is because it allows us to find where the y intercept is if we solve for it. Look at picture for work and answer. Hope this helps.

Consider a collection of envelopes consisting of 3 red ​, 3 blue ​, 1 green ​, and 2yellow . If three envelopes are selected at​ random, without​ replacement, determine the probability that at least one envelope is a red envelope.

Answers

Answer:

The probability is 31/35

Step-by-step explanation:

The area of the rectangular sheet is 500cm square. If the length of the sheet is 25cm, what is its width? Also find the perimeter of the rectangular sheet.​

Answers

Answer:

20cm Perimeter: 90

Step-by-step explanation:

Hope this helps!(^-^)

Step-by-step explanation:

area of rectangular sheet is 500 CM square

length =25cm

area =l×b

500cm2=25cm×b

500cm2÷25cm=b

20cm=b

b=20cm

again,

perimeter =2(l+b)

perimeter =2(25cm+20)

perimeter =2×45

perimeter =90cm

The ratio 124:111 is a blank comparison

Answers

Answer:

part to part

Step-by-step explanation:

Answer:person abov me

Step-by-step explanation:

There are 45 students who play a woodwind instrument in the school band. Of these, 18 play the saxophone. What percent of the woodwind musicians play the saxophone?

Answers

40% of students who play the saxophone
18/45= .4 = 4/10*10/10= 40/100= 40%

What is an equation of the line that passes through the points (6, -7)(6,−7) and (-6, 3)(−6,3)? Put your answer in fully reduced form.

Answers

Given:

A line passes through the points (6,-7) and (-6,3).

To find:

The equation of line.

Solution:

If a line passes through two points [tex](x_1,y_1)\text{ and }(x_2,y_2)[/tex], then the equation of line is

[tex]y-y_1=\dfrac{y_2-y_1}{x_2-x_1}(x-x_1)[/tex]

The line passes through the points (6,-7) and (-6,3). So, the equation of line is

[tex]y-(-7)=\dfrac{3-(-7)}{-6-6}(x-6)[/tex]

[tex]y+7=\dfrac{3+7}{-12}(x-6)[/tex]

[tex]y+7=\dfrac{10}{-12}(x-6)[/tex]

[tex]y+7=-\dfrac{5}{6}(x-6)[/tex]

Using distributive property, we get

[tex]y+7=-\dfrac{5}{6}(x)-\dfrac{5}{6}(-6)[/tex]

[tex]y+7=-\dfrac{5}{6}x+5[/tex]

Subtract 7 from both sides.

[tex]y=-\dfrac{5}{6}x+5-7[/tex]

[tex]y=-\dfrac{5}{6}x-2[/tex]

Therefore, the equation of line is [tex]y=-\dfrac{5}{6}x-2[/tex].

Please help! I’ll mark you as brainliest if correct!!!!

Answers

Answer:

             20

Step-by-step explanation:

The equation of shifted function y = ax² is y = a(x-h)²+k, where h tells us how many units we move left (h<0) or right (h>0) and k tells how many units up (k>0) or down (k<0)

y = x² - 20 = 1(x - 0)² + (-20)   ⇒  k = -20<0

So it's shifted 20 units down.

x^2 + 10x + 12
please help!!

Answers

Answer:

This cannot be simplified any further. That is the simplest you'll get.

What is meant by the term observed frequencies (O)?
a. The frequencies found in the population
b. The frequencies that are hypothesized for the population being examined
c. The frequencies calculated from the null hypothesis
d. The frequencies found in the sample

Answers

Answer:

The term observed frequencies are found in the sample.

Hence, option 'd' is correct.

Step-by-step explanation:

Unlike the expected frequency which is obtained based on prediction, the observed frequency is the actual frequency that is determined from the experiment.

Therefore, we conclude that

The term observed frequencies are found in the sample.

Hence, option 'd' is correct.

What expression is equivalent to (-18) - 64n

Answers

-18-64n

= (-2)×9 + (-2)×32n

Take (-2) common, we get

= (-2)( 9+32n)

Therefore,

-18-64n = (-2)(9+32n)

Answer:The other guy is right since this is a old question i wont answer it :P

Step-by-step explanation:

is one prime or composite?

Answers

It's neither prime or composite.

1 only has a single factor which is 1, so you can't really say.

One is a prime number because it can only be gotten in multiplication equation by using 1x1 to get 1! If it was 12 where multiple equations could get it like 3x4 then it would be composite!

Hope this helps, if not, comment below please!!!

Will give brainiest!

Answers

Answer:

680 oranges

15 levels

Step-by-step explanation:

Add 2, add 3, add 4, add 5.....

1+3+6+10+15+21+28+36+45+55+66+78+91+105+120=680

15 levels

He can’t add a 16th level, because it would have 136 oranges, which would put him over 800.

Answer:

15 levels, 680 oranges.

Step-by-step explanation:

Guess an check. The first 15 add to 680. The 16th is 136. 680+136=810, which is over 800.

I need help solving these ​

Answers

Answer:

m∠1 = 140°

m∠2 = 40°

m∠3 = 65°

m∠4 = 75°

m∠5 = 115°

Step-by-step explanation:

We will use a few different methods to find the angles:

A triangle's angles will always add up to 180°. With this information, we can find the last angle of the triangle on the left:

∠1+∠2+∠3=180°

60+80+∠3=180°

Let x represent the value of ∠3. Simplify addition:

[tex]140+x=180[/tex]

Subtract 140 from both sides:

[tex]140-140+x=180-140\\\\x=40[/tex]

The unknown angle is 40°. With this information, we can find the

m∠1:

m∠1 and the 40° we just found are supplementary angles, which means that their measures will add up to a total of 180°.

∠1+∠2=180°

Insert the value we know:

40°+∠2=180

Let x represent the value of ∠2. Subtract 40 from both sides:

[tex]40-40+x=180-40\\\\x=140[/tex]

There fore:

m∠1=140°

We can use this same rule to find the m∠2:

∠1+∠2=180°

or, we can use the vertical angles rule. The first angle we found (Which is 40°) is a vertical angle to m∠2, so they have the same value. Therefore:

m∠2=40°

To find m∠3, we need to find the other missing angle in the middle triangle. Use the supplementary angle rule, since the missing angle is supplementary to the angle that is 105°:

∠1+∠2=180°

Insert the known values, substituting x for the unknown angle:

[tex]x+105=180[/tex]

Subtract 105 from both sides:

[tex]x+105-105=180-105\\\\x=75[/tex]

The unknown angle is 75°. Now find m∠3, knowing that triangles add up to 180°:

m∠2+m∠3+75=180

Insert the m∠2, make m∠3 be x:

[tex]40+x+75=180[/tex]

Simplify addition:

[tex]115+x=180[/tex]

Subtract 115 from both sides:

[tex]115-115+x=180-115\\\\x=65[/tex]

Therefore:

m∠3=65°

To find m∠4, use the vertical angle rule.

Therefore:

m∠4=75°

To find m∠5, we could find all triangle measures of the least triangle, or we can use the following:

An exterior angle of a triangle is equal to the sum of the two opposite interior angles. The sum of exterior angle and interior angle is equal to 180 degrees.

The m∠5 is the exterior angle, and the opposite interior angles are 75° and 40°:

[tex]75+40=115[/tex]

Therefore:

m∠5=115°

:Done

Examine the system of equations.

y = negative one-fourth x minus 2

x = 4

What is the solution to the system?
(–3, –2)
(4, –3)
(4, –2)
(4, –1)

Answers

The answer is 4,-3

Irfcdxsaacd d

Answer:

4,-3

Step-by-step explanation:

Item 6
Question 1
You notice a hot air balloon descending. The elevation h (in feet) of the balloon is modeled by the function h(x)=-11x+330, where x is the time (in seconds) since you first noticed the hot air balloon.
Graph the function and specify its domain and range. Then interpret the slope and intercepts of the graph.

Answers

Answer:

Domain

[tex]x\in [0\,s,30\,s][/tex]

Range

[tex]h \in [0\,ft,330\,ft][/tex]

The h-Intercept represents the initial height of the balloon. The balloon has an initial height of 330 feet.

The x-Intercept represents the time when the balloon reaches the ground. The balloon takes 30 seconds to descend and reach the ground.

The slope represents the ratio of the change in the elevation of the balloon to the change in time. A slope of -11 means that balloon descends 11 feet per second.  

Step-by-step explanation:

Both the time (domain), measured in seconds, and the height (range), measured in feet, are positive variables. The hot air balloon start at a height above and descends to the ground. Which means that domain and range of the function are, respectively:

Now we find the upper bound of the height of the hot air balloon. If we know that [tex]t = 0\,s[/tex], then the upper bound is:

[tex]h(0) = -11\cdot (0)+330[/tex]

[tex]h(0) = 330\,ft[/tex]

Range

[tex]h \in [0\,ft,330\,ft][/tex]

Now we find the upper bound of time. If we know that [tex]h = 0\,ft[/tex]. then the upper bound is:

[tex]-11\cdot x +330 = 0[/tex]

[tex]11\cdot x = 330[/tex]

[tex]x = 30\,s[/tex]

Domain

[tex]x\in [0\,s,30\,s][/tex]

The h-Intercept represents the initial height of the balloon. The balloon has an initial height of 330 feet.

The x-Intercept represents the time when the balloon reaches the ground. The balloon takes 30 seconds to descend and reach the ground.

The slope represents the ratio of the change in the elevation of the balloon to the change in time. A slope of -11 means that balloon descends 11 feet per second.  

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