The width of a rectangle is three units less than the length if the area is 28 square units then find the dimensions of the rectangle
Let
width be xLength=x+3ATQ
[tex]\\ \sf \longmapsto Area=Length\times Width[/tex]
[tex]\\ \sf \longmapsto x(x+3)=28[/tex]
[tex]\\ \sf \longmapsto x^2+3x=28[/tex]
[tex]\\ \sf \longmapsto x^2+3x-28=0[/tex]
[tex]\\ \sf \longmapsto x^2+7x-4x-28=0[/tex]
[tex]\\ \sf \longmapsto x(x+7)-4(x+7)=0[/tex]
[tex]\\ \sf \longmapsto (x-4)(x+7)=0[/tex]
[tex]\\ \sf \longmapsto x=4\:or\:x=-7[/tex]
Ignore negative value[tex]\\ \sf \longmapsto Width=4units[/tex]
[tex]\\ \sf \longmapsto Length=4+3=7units[/tex]
An ice cream store determines the cost of its sundaes by using the formula C = 0.50s + 0.35n + 0.25t, where C is the total cost in dollars, s is the number of scoops of ice cream, n is the number of scoops of nuts, and t is the number of liquid toppings. A Nutty Sundae costs $3.55. It has 3 scoops of nuts and 2 different liquid toppings. How many scoops of ice cream are in this sundae?
Answer:
4 scoops of ice cream
Step-by-step explanation:
Plug in the total cost, number of scoops of nuts, and number of liquid toppings into the formula. Then, solve for s:
C = 0.50s + 0.35n + 0.25t
3.55 = 0.50s + 0.35(3) + 0.25(2)
3.55 = 0.50s + 1.05 + 0.5
3.55 = 0.50s + 1.55
2 = 0.50s
4 = s
So, the sundae had 4 scoops of ice cream.
Heather, a sociology major is interested in studying mass media topics. She is particularly interested in the percentage of mass media topics that relate to entertainment. Based on previous research, 72% of mass media topics relate to entertainment. She suspects this percent is different. During the process of hypothesis testing, she calculates a probability using the test statistic. What is the probability associated with the test statistic called
Answer:
Pvalue
Step-by-step explanation:
The Pvalue measure which takes up a value in the range 0 - 1 is a statistical measure used on hypothesis testing to measure the likelihood of obtaining result atleast as extreme as the outcome of the statistical hypothesis test, The Pvalue is used in hypothesis testing to make a case for the alternative hypothesis, which involves being compared with the α - value.
Lower p values favors the adoption of alternative depending on how extreme th α-value is. The Pvalue is dependent on the value if the test statistic.
Q-21: The regions of inequalities are also called:
A) Planes B) Lines C) Half planes D) None of these
Answer:
D ) none of these .. i think this help you
Can someone please help me with this
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Answer:
21. D
22. C
Step-by-step explanation:
21. The expansion of the given expression is ...
[tex]\displaystyle -\frac{1}{2}\left(-\frac{3}{2}x+6x+1\right)-3x=\frac{3}{4}x-3x-\frac{1}{2}-3x\\\\=\left(\frac{3}{4}-3-3\right)x-\frac{1}{2}=\boxed{-5\frac{1}{4}x-\frac{1}{2}}[/tex]
__
22. The least likely team to make the championship game is the one with the lowest probability.
3/8 < 1/2 < 2/3 < 4/5
The Bulldogs are least likely to play in the championship game.
If you were asked to measure the success of a campaign to fight for human rights, what criteria would you use?
Step-by-step explanation:
Many factors would be used to assess the effectiveness of a human rights campaign, including the following:
Social Influence. Direct Interpersonal Reach. Participant Observation. Reputation. Volume of Search & Interest. Website Traffic.
National Research.
Twenty-seven minus 3/2 of a number (x) os not mpre than 36. What is the number?
Answer:
-6
Step-by-step explanation:
27-3/2x=36
53-3x=72
3x=-18
x=-6
a principal of $1500 is invested at 5.5 interest compounded annually. how much will the investment be worth after 7 years
Answer:
Step-by-step explanation:
1500(1.055)^7= 2182.02
Question
Five people, each working 8 hours a day, can assemble 400 toys in a 5-day work week. What is the average
number of toys assembled per hour, per person?
Jorge plans to paint a bedroom wall that is shaped like a trapezoid. The bottom edge of the wall is 22.5 feet long, and the top edge of the wall is 9.5 feet long. If the wall is 8 feet tall, what is the area of the wall? Round your answer to the nearest hundredth if necessary.
Hot-dog buns come in packages of 10. Wieners come in
packages of 12. Barry would like to buy the smallest
number of hot-dog buns and wieners so that he will have
exactly 1 wiener per bun. How many packages of hot-dog
buns and wieners must he buy?
A 6 packages of buns, 5 packages of wieners
B 5 packages of buns, 5 packages of wieners
C 8 packages of buns, 7 packages of wieners
05 packages of buns, 4 packages of wieners
Answer:
A 6 Packages of buns and 5 packages of wieners.
Step-by-step explanation:
Because if you multiply 6x10 you get 60 and if you multiply 5x12 you get 60 exactly 1 wieners per bun
(2i+1)/(1+i) is equal to
Answer:
Step-by-step explanation:
(1 + 2i) / (1 + i) Rationalize the denominator.
(1 + 2i)(1+i) / (1 + i)(1-i) Remove the brarckets
(1 + i + 2i - 2) / (1 - i + i - i^2) Combine
-1 + 3i / (2) i^2 = - 1 in the denominator
A pole that is 3 m tall casts a shadow that is 1.23 m long. At the same time, a nearby building casts a shadow that is 42.75 m long. How tall is the building? round your answer to the nearest meter.
Answer:
Hello,
Just using the theorem of Thalès,
Step-by-step explanation:
Let say h the hight of the building
[tex]\dfrac{h}{3} =\dfrac{42.75}{1.23}\\\\h=104.268296...\approx{104(m)}[/tex]
The equation 8(y-3)= -40 is solved in several steps below. For each step, choose the reason that best justifies it.
Addition property of Equality
Subtraction Property of Equality
Multiplication property of equality
Division property of equality
simplifying
distributive property
Answer:
Step-by-step explanation:
The steps and their reasons for the equation 8(y - 3) = - 40 are given below.
What is the solution to the equation?The allocation of weights to the important variables that produce the calculation's optimum is referred to as a direct consequence.
The equation is given below.
8(y - 3) = - 40
Steps Reason
8(y - 3) = - 40 Given
8y - 24 = - 40 Distributive property
8y - 24 + 24 = - 24 + 24 Addition Property of Equality
8y = - 16 Simplifying
8y / 8 = - 16/8 Division property of equality
y = - 2 Simplifying
More about the solution of the equation link is given below.
https://brainly.com/question/545403
#SPJ2
the value of 2√4-3√27+√16+√225 is
Answer:
hope this help you
sorry if it is mistake
The The Laplace Transform of a function , which is defined for all , is denoted by and is defined by the improper integral , as long as it converges. Laplace Transform is very useful in physics and engineering for solving certain linear ordinary differential equations. (Hint: think of as a fixed constant) 1. Find (hint: remember integration by parts)
Answer:
a. L{t} = 1/s² b. L{1} = 1/s
Step-by-step explanation:
Here is the complete question
The The Laplace Transform of a function ft), which is defined for all t2 0, is denoted by Lf(t)) and is defined by the improper integral Lf))s)J" e-st . f(C)dt, as long as it converges. Laplace Transform is very useful in physics and engineering for solving certain linear ordinary differential equations. (Hint: think of s as a fixed constant) 1. Find Lft) (hint: remember integration by parts) A. None of these. B. O C. D. 1 E. F. -s2 2. Find L(1) A. 1 B. None of these. C. 1 D.-s E. 0
Solution
a. L{t}
L{t} = ∫₀⁰⁰[tex]e^{-st}t[/tex]
Integrating by parts ∫udv/dt = uv - ∫vdu/dt where u = t and dv/dt = [tex]e^{-st}[/tex] and v = [tex]\frac{e^{-st}}{-s}[/tex] and du/dt = dt/dt = 1
So, ∫₀⁰⁰udv/dt = uv - ∫₀⁰⁰vdu/dt w
So, ∫₀⁰⁰[tex]e^{-st}t[/tex] = [[tex]\frac{te^{-st}}{-s}[/tex]]₀⁰⁰ - ∫₀⁰⁰ [tex]\frac{e^{-st}}{-s}[/tex]
∫₀⁰⁰[tex]e^{-st}t[/tex] = [[tex]\frac{te^{-st}}{-s}[/tex]]₀⁰⁰ - ∫₀⁰⁰ [tex]\frac{e^{-st}}{-s}[/tex]
= -1/s(∞exp(-∞s) - 0 × exp(-0s)) + [tex]\frac{1}{s}[/tex] [[tex]\frac{e^{-st} }{-s}[/tex]]₀⁰⁰
= -1/s[(∞exp(-∞) - 0 × exp(0)] - 1/s²[exp(-∞s) - exp(-0s)]
= -1/s[(∞ × 0 - 0 × 1] - 1/s²[exp(-∞) - exp(-0)]
= -1/s[(0 - 0] - 1/s²[0 - 1]
= -1/s[(0] - 1/s²[- 1]
= 0 + 1/s²
= 1/s²
L{t} = 1/s²
b. L{1}
L{1} = ∫₀⁰⁰[tex]e^{-st}1[/tex]
= [[tex]\frac{e^{-st} }{-s}[/tex]]₀⁰⁰
= -1/s[exp(-∞s) - exp(-0s)]
= -1/s[exp(-∞) - exp(-0)]
= -1/s[0 - 1]
= -1/s(-1)
= 1/s
L{1} = 1/s
What are the new vertices of quadrilateral KLMN if the quadrilateral is translated two units to the right and four units upward?
A)
K′ = (–2,0), L′ = (1,0), M′ = (1,–3), N′ = (–2,–3)
B)
K′ = (–2,2), L′ = (1,2), M′ = (1,–1), N′ = (–2,–1)
C)
K′ = (–0,0), L′ = (3,0), M′ = (3,–1), N′ = (0,–1)
D)
K′ = (–2,–2), L′ = (1,–2), M′ = (1,–5), N′ = (–2,–5)
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Answer:
B) K′ = (–2,2), L′ = (1,2), M′ = (1,–1), N′ = (–2,–1)
Step-by-step explanation:
Translation 2 units right adds 2 to the x-coordinate.
Translation 4 units upward adds 4 to the y-coordinate.
The translation can be represented by the relation ...
(x, y) ⇒ (x +2, y +4)
__
You can choose the correct answer by looking at the translation of K.
K(-4, -2) ⇒ K'(-4+2, -2+4) = K'(-2, 2) . . . . . matches choice B
Ben consumes an energy drink that contains caffeine. After consuming the energy drink, the amount of caffeine in Ben's body decreases exponentially. The 10-hour decay factor for the number of mg of caffeine in Ben's body is 0.2722. What is the 5-hour growth/decay factor for the number of mg of caffeine in Ben's body
Answer:
The 5-hour decay factor for the number of mg of caffeine in Ben's body is of 0.1469.
Step-by-step explanation:
After consuming the energy drink, the amount of caffeine in Ben's body decreases exponentially.
This means that the amount of caffeine after t hours is given by:
[tex]A(t) = A(0)e^{-kt}[/tex]
In which A(0) is the initial amount and k is the decay rate, as a decimal.
The 10-hour decay factor for the number of mg of caffeine in Ben's body is 0.2722.
1 - 0.2722 = 0.7278, thus, [tex]A(10) = 0.7278A(0)[/tex]. We use this to find k.
[tex]A(t) = A(0)e^{-kt}[/tex]
[tex]0.7278A(0) = A(0)e^{-10k}[/tex]
[tex]e^{-10k} = 0.7278[/tex]
[tex]\ln{e^{-10k}} = \ln{0.7278}[/tex]
[tex]-10k = \ln{0.7278}[/tex]
[tex]k = -\frac{\ln{0.7278}}{10}[/tex]
[tex]k = 0.03177289938 [/tex]
Then
[tex]A(t) = A(0)e^{-0.03177289938t}[/tex]
What is the 5-hour growth/decay factor for the number of mg of caffeine in Ben's body?
We have to find find A(5), as a function of A(0). So
[tex]A(5) = A(0)e^{-0.03177289938*5}[/tex]
[tex]A(5) = 0.8531[/tex]
The decay factor is:
1 - 0.8531 = 0.1469
The 5-hour decay factor for the number of mg of caffeine in Ben's body is of 0.1469.
Find an equation of the line through the given pair of points. (-7,-5) and (-1,-9) The equation of the line is (Simplify your answer. Type an equation using x and y as the variables. Use integers or fractions for any numbers in the equation.) please help
Answer:
The equation of the line is y = -2/3x - 29/3
Step-by-step explanation:
The slope of these points (-7,-5) and (-1,-9) is m = -2/3
Once you plug that into the y = mx + b equation, you can see that the y-intercept is -29/3.
Put all of that into the y = mx + b equation and you'll get --> y = -2/3x - 29/3
There is only 3/4 cup of ice cream left. If 3 friends share the ice cream equally, how much ice cream will they each get?
Answer:
1/4 cup each
Step-by-step explanation:
Take the amount of ice cream and divide by 3
3/4÷ 3
Copy dot flip
3/4 * 1/3
Rewriting
3/3 * 1/4
1/4 cup each
Lines of symmetry give e the answer
Answer:
4
Step-by-step explanation:
There are 4 reflectional symmetry
A physical trainer decides to collect data to see if people are actually weight changing weight during the shelter in place. He believes there will not be a meaningful change in weight due to the shelter in place order. He randomly chooses a sample of 30 of his clients. From each client, he records their weight before the shelter in place order, and again 10 days after the order. A summary of the data is below.
The trainer claims, "on average, there is no difference in my clients' weights before and after the shelter in place order." Select the pair of hypotheses that are appropriate for testing this claim.
H0: µd = 0
H1: µd < 0 (claim)
H0: µd = 0 (claim)
H1: µd ≠ 0
H0: µd ≠ 0 (claim)
H1: µd = 0
H0: µd = 0 (claim)
H1: µd > 0
H0: µd = 0
H1: µd > 0 (claim)
H0: µd = 0
H1: µd ≠ 0 (claim)
H0: µd = 0 (claim)
H1: µd < 0
H0: µd ≠ 0
H1: µd = 0 (claim)
b) Select the choice that best describes the nature and direction of a hypothesis test for this claim.
This is a right-tail t-test for µd.
This is a right-tail z-test for µd.
This is a two-tail t-test for µd.
This is a two-tail z-test for µd.
This is a left-tail t-test for µd.
This is a left-tail z-test for µd.
c) Find the standardized test statistic for this hypothesis test. Round your answer to 2 decimal places.
d) Find the P-value for this hypothesis test. Round your answer to 4 decimal places.
e) Using your previous calculations, select the correct decision for this hypothesis test.
Fail to reject the alternative hypothesis.
Reject the alternative hypothesis.
Fail to reject the claim.
Reject the claim.
Fail to reject the null hypothesis.
Reject the null hypothesis.
f) Consider the following statements related to the trainer's claim. Interpret your decision in the context of the problem (ignoring the claim) and interpret them in the context of the claim.
Answer:
H0: µd = 0 (claim)
H1: µd ≠ 0
This is a two-tail t-test for µd
Step-by-step explanation:
This is a paired (dependent) sample test, with its hypothesis is written as :
H0: µd = 0
H1: µd ≠ 0
From the equality sign used in the hypothesis declaration, a not equal to ≠ sign in the alternative hypothesis is used for a two tailed t test
The data isn't attached, however bce the test statistic cannot be obtained. However, the test statistic formular for a paired sample is given as :
T = dbar / (Sd/√n)
dbar = mean of the difference ; Sd = standard deviation of the difference.
Find the 5 data points needed for a box plot of the given data set: { 8, 19, 11, 20, 2, 14, 17, 9, 15}
Give the answers in order from least to greatest.
Data Point 1:
Data Point 2:
Data Point 3:
Data Point 4:
Data Point 5:
Answers:
Data Point 1: 2 Data Point 2: 8.5 Data Point 3: 14 Data Point 4: 18 Data Point 5: 20The boxplot is shown below.
=========================================
Explanation:
What your teacher wants is the five number summary.
This consists of:
MinQ1MedianQ3MaxGiven in that exact order.
The given data set is { 8, 19, 11, 20, 2, 14, 17, 9, 15}
This sorts to {2, 8, 9, 11, 14, 15, 17, 19, 20}
From this sorted set, we see that 2 is the smallest item. So this is the min value. This is data point 1.
The max is the largest item, which in this case is 20, so this value goes in the box for data point 5.
---------------------
Count out the number of values in the sorted set. You should count out n = 9 items.
Because n is odd, this means the median is in slot n/2 = 9/2 = 4.5 = 5
The value in the 5th slot is 14 which is the median (data point 3).
-----------------------
Once you determine the median, break the sorted set up like so
L = {2, 8, 9, 11}
U = {15, 17, 19, 20}
L is the lower set of values smaller than the median
U is the upper set of values larger than the median
The median itself is not part of set L and not part of set U either. It's ignored entirely from this point on.
From here, we find the middle values of L and U
You should find that the middle value of L is (8+9)/2 = 17/2 = 8.5 which is the value of Q1 (data point 2)
And also, the middle value of set U is (17+19)/2 = 36/2 = 18 which is the value of Q3 (data point 4)
-----------------------
To wrap everything up, we have this five number summary
Min = 2Q1 = 8.5Median = 14Q3 = 18Max = 20These will determine the features of the boxplot as shown below.
In this case, there are no outliers.
Please help this is due at 11:59 and im really stuck.
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Answer:
B B C C A A
Step-by-step explanation:
If we number the equations 1 to 6 left to right, then we have ...
B - can be put (y = 2x)B - can be put (y = (1/9)x)C - other, not a proportional relationshipC - other, y = 5/x, an inversely proportional relationshipA - has the form, k = 0.04A - has the form, k = -11help with q25 please. Thanks.
First, I'll make f(x) = sin(px) + cos(px) because this expression shows up quite a lot, and such a substitution makes life a bit easier for us.
Let's apply the first derivative of this f(x) function.
[tex]f(x) = \sin(px)+\cos(px)\\\\f'(x) = \frac{d}{dx}[f(x)]\\\\f'(x) = \frac{d}{dx}[\sin(px)+\cos(px)]\\\\f'(x) = \frac{d}{dx}[\sin(px)]+\frac{d}{dx}[\cos(px)]\\\\f'(x) = p\cos(px)-p\sin(px)\\\\ f'(x) = p(\cos(px)-\sin(px))\\\\[/tex]
Now apply the derivative to that to get the second derivative
[tex]f''(x) = \frac{d}{dx}[f'(x)]\\\\f''(x) = \frac{d}{dx}[p(\cos(px)-\sin(px))]\\\\ f''(x) = p*\left(\frac{d}{dx}[\cos(px)]-\frac{d}{dx}[\sin(px)]\right)\\\\ f''(x) = p*\left(-p\sin(px)-p\cos(px)\right)\\\\ f''(x) = -p^2*\left(\sin(px)+\cos(px)\right)\\\\ f''(x) = -p^2*f(x)\\\\[/tex]
We can see that f '' (x) is just a scalar multiple of f(x). That multiple of course being -p^2.
Keep in mind that we haven't actually found dy/dx yet, or its second derivative counterpart either.
-----------------------------------
Let's compute dy/dx. We'll use f(x) as defined earlier.
[tex]y = \ln\left(\sin(px)+\cos(px)\right)\\\\y = \ln\left(f(x)\right)\\\\\frac{dy}{dx} = \frac{d}{dx}\left[y\right]\\\\\frac{dy}{dx} = \frac{d}{dx}\left[\ln\left(f(x)\right)\right]\\\\\frac{dy}{dx} = \frac{1}{f(x)}*\frac{d}{dx}\left[f(x)\right]\\\\\frac{dy}{dx} = \frac{f'(x)}{f(x)}\\\\[/tex]
Use the chain rule here.
There's no need to plug in the expressions f(x) or f ' (x) as you'll see in the last section below.
Now use the quotient rule to find the second derivative of y
[tex]\frac{d^2y}{dx^2} = \frac{d}{dx}\left[\frac{dy}{dx}\right]\\\\\frac{d^2y}{dx^2} = \frac{d}{dx}\left[\frac{f'(x)}{f(x)}\right]\\\\\frac{d^2y}{dx^2} = \frac{f''(x)*f(x)-f'(x)*f'(x)}{(f(x))^2}\\\\\frac{d^2y}{dx^2} = \frac{f''(x)*f(x)-(f'(x))^2}{(f(x))^2}\\\\[/tex]
If you need a refresher on the quotient rule, then
[tex]\frac{d}{dx}\left[\frac{P}{Q}\right] = \frac{P'*Q - P*Q'}{Q^2}\\\\[/tex]
where P and Q are functions of x.
-----------------------------------
This then means
[tex]\frac{d^2y}{dx^2} + \left(\frac{dy}{dx}\right)^2 + p^2\\\\\frac{f''(x)*f(x)-(f'(x))^2}{(f(x))^2} + \left(\frac{f'(x)}{f(x)}\right)^2 + p^2\\\\\frac{f''(x)*f(x)-(f'(x))^2}{(f(x))^2} +\frac{(f'(x))^2}{(f(x))^2} + p^2\\\\\frac{f''(x)*f(x)-(f'(x))^2+(f'(x))^2}{(f(x))^2} + p^2\\\\\frac{f''(x)*f(x)}{(f(x))^2} + p^2\\\\[/tex]
Note the cancellation of -(f ' (x))^2 with (f ' (x))^2
------------------------------------
Let's then replace f '' (x) with -p^2*f(x)
This allows us to form ( f(x) )^2 in the numerator to cancel out with the denominator.
[tex]\frac{f''(x)*f(x)}{(f(x))^2} + p^2\\\\\frac{-p^2*f(x)*f(x)}{(f(x))^2} + p^2\\\\\frac{-p^2*(f(x))^2}{(f(x))^2} + p^2\\\\-p^2 + p^2\\\\0\\\\[/tex]
So this concludes the proof that [tex]\frac{d^2y}{dx^2} + \left(\frac{dy}{dx}\right)^2 + p^2 = 0\\\\[/tex] when [tex]y = \ln\left(\sin(px)+\cos(px)\right)\\\\[/tex]
Side note: This is an example of showing that the given y function is a solution to the given second order linear differential equation.
Thank you guys fir the help
Complete the proof and rewrite the statements.
Given :
ABC is an isosceles triangle in which AC = BC
CD ⊥ AB
Prove : AD = BD
Statement Reason
i) AC = BC Given
ii) ԼCDA = _______ Right angle
iii) CD = CD Common side
iv) ΔADC ≅ Δ BDC _______ test
v) AD = BD CPCT
Answer:
Step-by-step explanation:
(ii) right angle becuase perpendicular
iv) congruent because <b=<a (opp ang in isc.tria. is equal)
since ΔADC ≅ Δ BDC, AB=BD
What is the maximum of f(x)= sin(x)?
-2π
-1
1
2π
Answer:
1
Step-by-step explanation:
the maximum of f(X)=sin(X) is 1
Find f′ in terms of g′
f(x)=x2g(x)
Select one:
f′(x)=2xf′(x)+2xg′(x)
f′(x)=2xg′(x)
f′(x)=2x+g′(x)
f′(x)=x2g(x)+2x2g′(x)
f′(x)=2xg(x)+x2g′(x)
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Answer:
(e) f′(x)=2xg(x)+x²g′(x)
Step-by-step explanation:
The product rule applies.
(uv)' = u'v +uv'
__
Here, we have u=x² and v=g(x). Then u'=2x and v'=g'(x).
f(x) = x²·g(x)
f'(x) = 2x·g(x) +x²·g'(x)
A geologist has collected 5 specimens of basaltic rock and 7 specimens of granite. The geologist instructs a laboratory assistant to randomly select 9 of the specimens for analysis.
Let X= the number of granite specimens selected for analysis.
Note: Take 10 decimal places after the ".", if the answer is a fraction, enter the fraction (a/b). Use a period (.) not a comma (,) for decimals.
a) Compute EX = ?; Var(X) = ?
b) Compute P(X<6) = ?
c) What is the probability that all specimens of one of the two types of rock are selected for analysis?
P(all specimens of one of the two types of rock are selected for analysis) = ?
The rocks are chosen without replacement, which means that the hypergeometric distribution is used to solve this question. First we get the parameters, and then we answer the questions. From this, we get that:
[tex]E(X) = 5.25, Var(X) = 0.5966[/tex]P(X < 6) = 0.9545P(all specimens of one of the two types of rock are selected for analysis) = 0.2046.Hypergeometric distribution:
The probability of x successes is given by the following formula:
[tex]P(X = x) = h(x,N,n,k) = \frac{C_{k,x}*C_{N-k,n-x}}{C_{N,n}}[/tex]
In which:
x is the number of successes.
N is the size of the population.
n is the size of the sample.
k is the total number of desired outcomes.
Combinations formula:
[tex]C_{n,x}[/tex] is the number of different combinations of x objects from a set of n elements, given by the following formula.
[tex]C_{n,x} = \frac{n!}{x!(n-x)!}[/tex]
The mean and the variance are:
[tex]\mu = \frac{nk}{N}[/tex]
[tex]\sigma^2 = \frac{nk(N-k)(N-n)}{N^2(N-1)}[/tex]
We have that:
5 + 7 = 12 rocks, which means that [tex]N = 12[/tex]
9 are chosen, which means that [tex]n = 9[/tex]
7 are granite, which means that [tex]k = 7[/tex]
Question a:
[tex]E(X) = \mu = \frac{9\times7}{12} = 5.25[/tex]
[tex]Var(X) = \sigma^2 = \frac{9\times7(12-7)(12-9)}{12^2(12-1)} = 0.5966[/tex]
Thus:
[tex]E(X) = 5.25, Var(X) = 0.5966[/tex]
Question b:
Since there are only 5 specimens of basaltic rock, at least 9 - 5 = 4 specimens of granite are needed, which means that:
[tex]P(X < 6) = P(X = 4) + P(X = 5) + P(X = 6)[/tex]
In which
[tex]P(X = x) = h(x,N,n,k) = \frac{C_{k,x}*C_{N-k,n-x}}{C_{N,n}}[/tex]
[tex]P(X = 4) = h(4,12,9,7) = \frac{C_{7,4}*C_{5,5}}{C_{12,9}} = 0.1591[/tex]
[tex]P(X = 5) = h(5,12,9,7) = \frac{C_{7,5}*C_{5,4}}{C_{12,9}} = 0.4773[/tex]
[tex]P(X = 6) = h(6,12,9,7) = \frac{C_{7,6}*C_{5,3}}{C_{12,9}} = 0.3181[/tex]
Thus
[tex]P(X < 6) = P(X = 4) + P(X = 5) + P(X = 6) = 0.1591 + 0.4773 + 0.3181 = 0.9545[/tex]
So P(X < 6) = 0.9545.
Question c:
5 of basaltic and 4 of granite: 0.1591 probability.
7 of granite is P(X = 7), in which
[tex]P(X = 7) = h(7,12,9,7) = \frac{C_{7,7}*C_{5,2}}{C_{12,9}} = 0.0455[/tex]
0.1591 + 0.0455 = 0.2046, thus:
P(all specimens of one of the two types of rock are selected for analysis) = 0.2046.
A similar question is found at https://brainly.com/question/24008577