Answer:
[tex]Perimeter = 14 + 7\sqrt{2}[/tex]
Step-by-step explanation:
Given:
Area of the square = 49 in²
Required
Determine the perimeter of the one of the congruent triangles
First, we'll determine the length of the square;
[tex]Area = Length * Length[/tex]
Substitute 49 for Area
[tex]49 = Length * Length[/tex]
[tex]49 = Length^2[/tex]
Take Square root of both sides
[tex]7 = Length[/tex]
[tex]Length = 7[/tex]
When the square is divided into two equal triangles through the diameter;
2 sides of the square remains and the diagonal of the square forms the hypotenuse of the triangle;
Calculating the diagonal, we have;
[tex]Hypotenuse^2 = Length^2 + Length^2[/tex] -- Pythagoras Theorem
[tex]Hypotenuse^2 = 7^2 + 7^2[/tex]
[tex]Hypotenuse^2 = 2(7^2)[/tex]
Take square root of both sides
[tex]Hypotenuse = \sqrt{2} * \sqrt{7^2}[/tex]
[tex]Hypotenuse = \sqrt{2} * 7[/tex]
[tex]Hypotenuse = 7\sqrt{2}[/tex]
The perimeter of one of the triangles is the sum of the 2 Lengths and the Hypotenuse
[tex]Perimeter = Length + Length + Hypotenuse[/tex]
[tex]Perimeter = 7 + 7 + 7\sqrt{2}[/tex]
[tex]Perimeter = 14 + 7\sqrt{2}[/tex]
-15≤-3c plz helpppppppppp
Answer:
5 ≥ c
Step-by-step explanation:
-15≤-3c
Divide each side by -3, remembering to flip the inequality
-15/-3 ≤ -3c/-3
5 ≥ c
Answer:
c ≤ 5
Step-by-step explanation:
Since you have to divide both sides of the equation by a negative number, you have to flip the equality sign.
-15 ≤ -3c
(-15)/(-3) ≤ (-3c)/-3
5 ≥ c
c ≤ 5
HELP number 12 pls i do nor have long more
Answer:
Dian has $250 originally.
Step-by-step explanation:
Let the total money Dian has originally = $S
Dian gave [tex]\frac{2}{5}[/tex] of her total money to Justin,
Money given to Justin = [tex]\frac{2}{5}(\text{S})[/tex]
Money left with Dian = S - [tex]\frac{2}{5}(\text{S})[/tex]
= [tex]\frac{\text{5S-2S}}{5}[/tex]
= [tex]\frac{3S}{5}[/tex]
Since Dian has $150 left then the equation will be,
[tex]\frac{3S}{5}=150[/tex]
S = [tex]\frac{150\times 5}{3}[/tex]
S = $250
Therefore, Dian has $250 originally.
How would 2X - 2Y - 6 = 0 be
written in slope-intercept form?
A. 2X - 2Y = 6
B. -2Y = 2X = 6
C. Y=X - 3
D. Y = -2X - 3
E. Y = x + 3
Answer:
D. Y= -2x - 3
Step-by-step explanation:
The reason the answer is D is because it is the reverse form of standard. D shows that the form of slope-intercept for is y=mx + b.
Answer:
C. Y=X - 3
Step-by-step explanation:
[tex]2X - 2Y - 6 = 0\\\mathbf{y=mx+b}\:\mathrm{is\:the\:slope\:intercept\:form\:of\:a\:line\:where}\: \mathbf{m}\:\mathrm{is\:the\:slope\:and}\:\mathbf{b}\:\mathrm{is\:the}\:\mathbf{y}\:\mathrm{intercept}\\\mathrm{For\:a\:line\:in\:the\:form\:of\:}\mathbf{y=mx+b}\mathrm{,\:the\:slope\:is}\:\mathbf{m}\:\mathrm{and}\:\mathbf{y}\:\mathrm{intercept\:is}\:\mathbf{b}\\\\Y=X-3[/tex]
What is the missing segment?
Answer:
78.
Step-by-step explanation:
12 / (48-12) = 26 / x
12/36 = 26/x
1/3 = 26/x
x = 26*3 = 78.
Please help!! Which inequality is graphed on the coordinate plane?
Answer:
The correct answer that corresponds with that graph is B: y ≤-3x+2.
Step-by-step explanation:
1) First we need to figure out what kind of symbol the line is, greater or less than equations (< , >) then the line are dotted,and if its greater than or equal to or less than or equal to equations ( ≤, ≥) since the line are solid.
2) Now we need to figure out which side should be shaded, if the symbol is a less than or a less than or equal to then the shaded side should be on the left, if the symbol is a greater than or a greater than or equal then the shaded side should be on the right.
In this case we have a solid line and a shaded left side which mean the symbol that been used here is a less than or equal to symbol ( ≤ ).
So our answer is B: y ≤-3x+2.
Remember:
- greater or less than equations (< , >) = dotted line
- greater than or equal to or less than or equal to equations ( ≤, ≥) = solid line
- less than or a less than or equal to = shaded left side
- greater than or greater than or equal to = shaded right side
A certain article indicates that in a sample of 1,000 dog owners, 680 said that they take more pictures of their dog than of their significant others or friends, and 490 said that they are more likely to complain to their dog than to a friend. Suppose that it is reasonable to consider this sample as representative of the population of dog owners.
(a) Construct a 90% confidence interval for the proportion of dog owners who take more pictures of their dog than of their significant others or friends. (Use a table or technology. Round your answers to three decimal places.)
(______),(_________)
(b) Construct a 95% confidence interval for the proportion of dog owners who are more likely to complain to their dog than to a friend. (Use a table or technology. Round your answers to three decimal places.)
(_______),(_______)
Answer: a) a 90% confidence interval for the proportion of dog owners who take more pictures of their dog than of their significant others or friends is (0.656,0.704).
b) a 95% confidence interval for the proportion of dog owners who are more likely to complain to their dog than to a friend is (0.459,0.521).
Step-by-step explanation:
Confidence interval for a population proportion is given by:-
[tex]\hat{p}\pm z(\sqrt{\dfrac{\hat{p}(1-\hat{p})}{n}})[/tex]
, where [tex]\hat{p}[/tex] = sample proportion , n= sample size, z= critical z-value.
As per given,
a) n=1000
Sample proportion of dog owners say they take more pictures of their dog than of their significant others or friends =[tex]\hat{p}=\dfrac{680}{1000}=0.68[/tex]
critical value for 90% confidence = 1.645 [By table]
A 90% confidence interval for the proportion of dog owners who take more pictures of their dog than of their significant others or friends.
[tex]0.68\pm (1.645)\sqrt{\dfrac{0.68(1-0.68)}{1000}}\\\\\approx0.68\pm0.024=(0.68-0.024,0.68+0.024)=(0.656,0.704)[/tex]
Hence, a 90% confidence interval for the proportion of dog owners who take more pictures of their dog than of their significant others or friends is (0.656,0.704).
b) Sample proportion of dog owners say they are more likely to complain to their dog than to a friend =[tex]\hat{p}=\dfrac{490}{1000}=0.49[/tex]
critical value for 95% confidence = 1.96 [By table]
A 95% confidence interval for the proportion of dog owners who are more likely to complain to their dog than to a friend:
[tex]0.49\pm (1.96)\sqrt{\dfrac{0.49(1-0.49)}{1000}}\\\\\approx0.49\pm0.031=(0.49-0.031,0.49+0.031)=(0.459,0.521)[/tex]
Hence, a 95% confidence interval for the proportion of dog owners who are more likely to complain to their dog than to a friend is (0.459,0.521).
Use identities to find values of the sine and cosine functions of the function for the angle measure
a. theta, given that cos2theta=28/53 and 0theta < theta < 90degrees
b. 2theta, given sin theta= - sqrt 7 over 5 and cos theta > 0
c. 2x, given tan x=2 and cos x<0
Answer:
Step-by-step explanation:
a) Given cos2theta=28/53 and 0degrees< theta < 90degrees
From cos2theta=28/53
[tex]2\theta = cos^{-1}\frac{28}{53}[/tex]
[tex]2\theta = cos^{-1}0.5283\\ \\2\theta = 58.12\\\\Dividing\ both \ sides\ by \ 2\\\\\frac{2\theta}{2} = \frac{58.12}{2}\\ \\\theta = 29.06^0[/tex]
b) Given
[tex]sin\theta = \frac{-\sqrt{7} }{5} \\\\\theta = sin^{-1} \frac{-\sqrt{7} }{5}\\\\\\\theta = sin^{-1} \frac{-2.6458}{5}\\\\\theta = sin^{-1} -0.5292\\\\\theta = -31.95^0[/tex]
If cos theta [tex]\gneq[/tex] 0, this means we need to look for the quadrant where sin is negative and cos is positive. That will be the fourth quadrant. In the fourth quadrant, theta = 360 - 31.95° = 328.05°
2theta = 2 * 328.05
2theta = 656.1°
c) Given tan x=2 and cos x<0, lets find the angle of x first.
If tan x = 2
x = tan^-1 2
x = 63.4°
Sine cos is less than 0, then we need to find the angle of x where tan is positive and cos is negative. That will be the third quadrant. In the third quadrant, ew value of x = 180+63.4
x = 243.4°
Since we are to find 2x,
2x = 2(243.4)
2x = 486.8°
for f(x)=1/x-5 and g(x)=x^2+2 find the expression for g(x) and substitute the value of g(x) into the function in place of x to find the value of f(g(x))
Answer:
f(x) = (1/x) - 5
g(x) = x^2 + 2
=> f[g(x)] = [1/(x^2 +2)] - 5
The letters G, E, N, I, D, S are placed in a bag. What is the probability that the letters are randomly pulled from the bag in the order that spells DESIGN?
Answer as a fraction = 1/5040
Answer in decimal form (approximate) = 0.000198
Answer in percentage form (approximate) = 0.0198%
=========================================================
Explanation:
There is only one ordering of the letters to get DESIGN out of 5040 different permutations. The 5040 comes from the fact that 7*6*5*4*3*2*1 = 5040. In shorthand notation, use factorials to say 7! = 5040. Notice how we started with 7 and counted down until reaching 1, multiplying all along the way. You could use the nPr permutation formula to get the same result of 5040 (use n = 7 and r = 7).
So because we have 1 way to order the letters (getting DESIGN) out of 5040 ways total, this means the probability is the fraction 1/5040. Use your calculator to find that 1/5040 = 0.000198 approximately. Move the decimal over 2 spots to the right to convert 0.000198 to 0.0198%
State the degrees of freedom error in each of the following tests. (a) A consultant measures job satisfaction in a sample of 14 supervisors, 14 managers, and 14 executives at a local firm. (b) A researcher tests how nervous public speakers get in front of a small, medium, or large audience. Ten participants are randomly assigned to each group. (c) A high school counselor has 8 students in each of five classes rate how much they like their teacher.
Answer:
.
Step-by-step explanation:
What are some key words used to note addition operations?
Answer:
The correct answer is
For addition, Caulleen used the words total, sum, altogether, and increase. But we could also have used the words combine, plus, more than, or even just the word "and". For subtraction, Caulleen used the words, fewer than, decrease, take away, and subtract. We also could have used less than, minus, and difference.
Step-by-step explanation:
hope this helps u!!!
What is the solution of log3(3x+2)= log3 (4x-6)?
Answer:
x=8 i got it right on my homework on khan academy
Step-by-step explanation:
Answer: Using logarithms to solve you will get x = 8
A magazine article states that the mean weight of one-year-old boys is the same as that of one-year-old girls. Does the confidence interval contradict this statement? The confidence interval this statement
Answer:
Yes, the confidence interval contradict this statement.
Step-by-step explanation:
The complete question is attached below.
The data provided is:
[tex]n_{1}=318\\n_{2}=297\\\bar x_{1}=25\\\bar x_{2}=24.1\\s_{1}=3.6\\s_{2}=3.8[/tex]
Since the population standard deviations are not provided, we will use the t-confidence interval,
[tex]CI=(\bar x_{1}-\bar x_{2})\pm t_{\alpha/2, (n_{1}+n_{2}-2)}\cdot s_{p}\cdot\sqrt{\frac{1}{n_{1}}+\frac{1}{n_{2}}}[/tex]
Compute the pooled standard deviation as follows:
[tex]s_{p}=\sqrt{\frac{(n_{1}-1)s_{1}^{2}+(n_{2}-1)s_{2}^{2}}{n_{1}+n_{2}-2}}=\sqrt{\frac{(318-1)(3.6)^{2}+(297-1)(3.8)^{2}}{318+297-2}}=2.9723[/tex]
The critical value is:
[tex]t_{\alpha/2, (n_{1}+n_{2}-2)}=t_{0.05/2, (318+297-2)}=t_{0.025, 613}=1.962[/tex]
*Use a t-table.
The 95% confidence interval is:
[tex]CI=(\bar x_{1}-\bar x_{2})\pm t_{\alpha/2, (n_{1}+n_{2}-2)}\cdot s_{p}\cdot\sqrt{\frac{1}{n_{1}}+\frac{1}{n_{2}}}[/tex]
[tex]=(25-24.1)\pm 1.962\times 2.9723\times \sqrt{\frac{1}{318}+\frac{1}{297}}\\\\=0.90\pm 0.471\\\\=(0.429, 1.371)\\\\\approx (0.43, 1.37)[/tex]
The 95% confidence interval for the difference between the mean weights is (0.43, 1.37).
To test the magazine's claim the hypothesis can be defined as follows:
H₀: There is no difference between the mean weight of 1-year old boys and girls, i.e. [tex]\mu_{1}-\mu_{2}=0[/tex].
Hₐ: There is a significant difference between the mean weight of 1-year old boys and girls, i.e. [tex]\mu_{1}-\mu_{2}\neq 0[/tex].
Decision rule:
If the confidence interval does not consists of the null value, i.e. 0, the null hypothesis will be rejected.
The 95% confidence interval for the difference between the mean weights does not consists the value 0.
Thus, the null hypothesis will be rejected.
Conclusion:
There is a significant difference between the mean weight of 1-year old boys and 1-year old girls.
Solve the equation for x 5x-(4x-1)=2 A 1/9 B -1 C -1/9 D 1
Answer:
D
Step-by-step explanation:
Select the correct answer. Sarah wants to print copies of her artwork. At the local print shop, it costs her $1 to make 5 copies and $5 to make 25 copies. How much would it cost Sarah to make 100 copies? A. $15 B. $20 C. $25 D. $30
$1 = 5copies means
$5 = 25 copies obviously
then
$x = 100 copies
100 / 5 = $x
so she needs
$20
The cost of printing 100 copies of artwork is $20.
What is a unitary method?A unitary method is a mathematical way of obtaining the value of a single unit and then deriving any no. of given units by multiplying it with the single unit.
Suppose 2 pens cost $10, So the cost of 1 pen is (10/2) = $5.
From this unitary cost of pens, we can determine the cost of any no. of pens by multiplying the unit cost by the no. of pens.
Given, The cost of printing 5 artworks is $1.
∴ The cost of printing 100 copies is $(100/5),
= $20.
learn more about the unitary method here :
https://brainly.com/question/22056199
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If Joe drives 50 mph for 0.5 hours and then 60 mph for 1.5 hours, then how far did he drive?
Answer:
115 mi
Step-by-step explanation:
speed = distance/time
distance = speed * time
0.5 hours at 50 mph
distance = 50 mph * 0.5 h = 25 mi
1.5 hours at 60 mph
distance = 60 mph * 1.5 h = 90 mi
total distance = 25 mi + 90 mi = 115 mi
Find y................
Answer:
[tex] y = 3 [/tex]
Step-by-step explanation:
Given the above right angled triangle, we would use a trigonometric ratio formula to find y.
Given angle = 30°
Hypotenuse = 6
Opposite side = y
Solve for y using the trigonometric ratio formula as follows:
[tex] sin(X) = \frac{opposite}{hypotenuse} [/tex]
[tex] sin(30) = \frac{y}{6} [/tex]
Multiply both sides by 6
[tex] sin(30)*6 = \frac{y}{6}*6 [/tex]
[tex] 0.5*6 = y [/tex]
[tex] 3 = y [/tex]
[tex] y = 3 [/tex]
What is the volume of air that the beach ball will hold?
Answer:
In order to solve this problem, we need to know the volume of a sphere.
The volume of a sphere is (4/3)pir^3
In this case our r value, or radius, is 30cm.
If we plug in 30cm to the equation like so:
(4/3)pi(30)^3
The answer is 113097 cm^3 of air
Hope you understand
The equation of the line of best fit is y=15.621x+8.83 Based on the line of best fit, Approximately how many pages are predicted To be in a book with eight chapters
Answer:
[tex] y = 15.621x +8.83[/tex]
We assume that y represent the number of pages predicted and x the number of chapters.
And we want to find the predicted value for a book of x =8 chapters. S replacing we got:
[tex] y = 15.621*8 + 8.83= 133.798[/tex]
And we can conclude that approximately we would have between 133 and 134 pages for a book of 8 chapters
Step-by-step explanation:
For this case we have the following model given:
[tex] y = 15.621x +8.83[/tex]
We assume that y represent the number of pages predicted and x the number of chapters.
And we want to find the predicted value for a book of x =8 chapters. S replacing we got:
[tex] y = 15.621*8 + 8.83= 133.798[/tex]
And we can conclude that approximately we would have between 133 and 134 pages for a book of 8 chapters
If the triangle on the grid below is translated by using the rule (x, y) right-arrow (x + 5, y minus 2), what will be the coordinates of B prime?
Answer:
Option (2)
Step-by-step explanation:
If a point having coordinates (x, y) is translated by 'h' units right and 'k' units down,
New coordinates of the point will be,
(x, y) → [(x + h), (y - k)]
Coordinates of the vertices of the given triangle ABC are,
A(-1, 0), B(-5, 0) and C(-1, 2)
If this triangle is shifted 5 units right and 2 units down then the coordinates of point B will be,
B(-5, 0) → B'[(-5 + 5), (0 -2)]
→ B'(0, -2)
Therefore, coordinates of vertex B' will be (0, -2).
Option (2) will be the answer.
Answer:
(0,-2) is Correct
Have a Blessed day!
i will give brainliest and 50 points pls help ASP
pls can u show how to work this out thx !!! : )
its a simultaneous equation
Answer:
x = 3
y = -2
Step-by-step explanation:
Given:
8x - 3y = 30 ..................(1)
3x + y = 7 .......................(2)
Eliminate y by adding (1)+3*(2)
8x-3y + 3*( 3x+y) = 30 + 3*7
8x + 9x -3y + 3y = 51
17x = 51
x = 3 .....................(3)
substitute (3) in (2)
3(3) + y = 7
y = 7-9 = -2
y = -2 ....................(4)
Answer:
Step-by-step explanation:
[tex]8x-3y=30\\y=7-3x\\\\8x-3(7-3x)=30\\8x-21+9x=30\\17x=51\\x=3\\\\y=7-3(3)\\y=7-9\\y=-2[/tex]
Write the equation of the line in slope intercept form that passes through the points (4,-2) and (2,-1)
Answer:
y + 2 = (-1/2)(x - 4)
Step-by-step explanation:
Let's move from (2, -1) to (4, -2) and measure the changes in x and y. x increases by 2 units from 2 to 4, and y decreases by 1 unit from -1 to -2. Thus, the slope of the line connecting the two points is m = rise / run =
-1
--- = (-1/2).
2
Using the point-slope formula, we get:
y + 2 = (-1/2)(x - 4)
From which sphere of earth did this food did this food originate
Answer:
I'm not entirely sure what you are asking, could you comment on this answer the full question so I can edit this question to provide you an answer?
Answer: biosphere
Step-by-step explanation:
I am not sure what picture you are looking at but if it is 3 barbeque chicken legs in one image than this is your answer. The reason being that chickens can only be found on land and the land is considered part of the biosphere because bio = life
A copy machine makes 153 copies in 4 minutes 15 seconds how many copies does it make per minute
Answer:
36 copies.
Step-by-step explanation:
4mins 15 seconds is the same as 4+1/4 minsutes. Since 1 minute is less than 4+1/4minutes and 4+1/4 minutes produces 153 copies. 1 minute will produce less.
(1÷4+1/4)×153
= 36 copies.
There is a stack of 10 cards, each given a different number from 1 to 10. Suppose we select a card randomly from the stack, replace it, and then randomly select another card. What is the probability that the first card is an odd number and the second card is greater than 7
====================================================
Explanation:
Here's our sample space
{1,2,3,4,5,6,7,8,9,10}
This is the set of all possible outcomes.
We see that {1,3,5,7,9} are odd. We have 5 odd numbers out of 10 total. The probability of getting an odd number is therefore 5/10 = 1/2. Let A = 1/2 as we'll use it later.
After we select the first card and put it back (or replace it with a copy), the stack of cards is the same as before we made that first selection. So the sample space hasn't changed. The set of values greater than 7 is {8,9,10}. We have 3 items in here out of 10 total. The probability of getting a value larger than 7 is 3/10. Let B = 3/10.
Multiply the values of A and B to get the answer
A*B = (1/2)*(3/10) = 3/20
This represents the probability of getting an odd number on the first selection, and a second card that is larger than 7. This only applies if a replacement is made on the first card. Otherwise, 3/10 would be different.
How many solutions does the following equation have? 14(z+3)=14z+21
Answer:
No solutions
Step-by-step explanation:
14(z + 3) = 14z + 21
Expand brackets.
14z + 42 = 14z + 21
Subtract 14z on both sides.
42 = 21
There are no solutions.
Answer:
No solution
Step-by-step explanation:
First, We have to simplify the right side.
Distribute 14, 14z+42.
Now the equation stands as 14z+42=14z+21
Subtract 14z from both sides,
this makes it 42=21.
We know when the solution is #=#, our answer is no solution.
round 235,674 to the nearest thousand
Answer:
236,000
Step-by-step explanation:
When rounding to thousands, if the hundred is 500 or over, you round up. If it is less, round down.
Answer:
Hey! The answer is 236,000.... steps will be below!
Step-by-step explanation:
Since there is 5,674 it is more closer to 6,000 than 5,000
So we change the number to 236,000
ANSWER TO YOUR QUESTION: 236,000
Hope this helps! :)
⭐️Have a wonderful day!⭐️
Write a system of equations in x and y describing the situation. Do not solve the system.
Keiko has a total of $5500, which she has invested in two accounts. The larger account is $700 greater than the smaller account. (Let x be the amount of money in the
larger account and y be the amount of money in the smaller account.)
Choose a system of equations describing the situation,
X+ y + 5500 = 0
x+y=5500
X= y + 700
X-y+ 700 = 0
O
2x = 5500
2x + 2y = 5500
x-y=700
x- y = 700
Lacey's mom makes her a birthday cake in the shape of an "L" . Lacey loves frosting, so her mom covers the entire outside of the cake in frosting, even the bottom of the cake. How much space does Lacey's mom cover in frosting? cm2\text{cm}^2cm2start text, c, m, end text, squared
Answer:
1360cm²
Step-by-step explanation:
Since the shape of the cake is in L shape, we can divide the cake in to rectangles..
The amount of space covered by the frosting = The sum of the areas of the sides that we can find in this L shaped cake diagram.
The sides of this cake, are shaped like a rectangle.
Hence, Area of a Rectangle = Length × Width
a) Side 1 = Rectangle on the left
Area of a Rectangle = Length × Breadth
Length = 30cm
Breadth =10cm
Area = 30 × 10 = 300cm²
Since we have another side with this measurement/ dimensions also,
Side 2 = 300cm²
Side 3 = The front face of the cube by the right
Area of a Rectangle = Length × Breadth
Length = 22cm - 10cm = 12cm
Breadth =10cm
Area = 12 × 10 = 120cm²
Likewise, we have the another side with the same dimensions as well
Hence, Side 4 = 120cm²
Side 5
30 × 5 = 150cm²
Side 6
10 × 5 = 50cm²
Side 7
20 × 5 = 100cm²
Side 8
22cm × 5 cm = 110cm²
Side 9
10cm × 5cm = 50cm²
Side 10
12cm × 5cm = 60cm²
The amount of space covered by the frosting = Area of Sides( 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10)
= (300 + 300 + 120 + 120 + 150 + 50 + 100 + 110 + 50 + 60) cm²
= 1360cm²
Suppose the sediment density (g/cm) of a randomly selected specimen from a certain region is normally distributed with mean 2.68 and standard deviation 0.92.
A. If a random sample of 25 specimens is selected, what is theprobability that the sample average sediment density is at most3.00? Between 2.68 and 3.00
B. How large a sample size would be required to ensure thatthe first probability in part (a) is at least .99 ?
Answer:
The sample size must be 45 large enough that would ensure that the first probability in part (a) is at least 0.99.
Step-by-step explanation:
We are given that the sediment density (g/cm) of a randomly selected specimen from a certain region is normally distributed with mean 2.68 and standard deviation 0.92.
Let [tex]\bar X[/tex] = sample average sediment density
The z-score probability distribution for the sample mean is given by;
Z = [tex]\frac{\bar X-\mu}{\frac{\sigma}{\sqrt{n} } }[/tex] ~ N(0,1)
where, [tex]\mu[/tex] = population mean = 2.68
[tex]\sigma[/tex] = population standard deviation = 0.92
n = sample of specimens = 25
(a) The probability that the sample average sediment density is at most 3.00 is given by = P([tex]\bar X[/tex] [tex]\leq[/tex] 3.00)
P([tex]\bar X[/tex] [tex]\leq[/tex] 3.00) = P( [tex]\frac{\bar X-\mu}{\frac{\sigma}{\sqrt{n} } }[/tex] [tex]\leq[/tex] [tex]\frac{3.00-2.68}{\frac{0.92}{\sqrt{25} } }[/tex] ) = P(Z [tex]\leq[/tex] 1.74) = 0.9591
The above probability is calculated by looking at the value of x = 1.74 in the z table which has an area of 0.9591.
Also, the probability that the sample average sediment density is between 2.68 and 3.00 is given by = P(2.68 < [tex]\bar X[/tex] < 3.00)
P(2.68 < [tex]\bar X[/tex] < 3.00) = P([tex]\bar X[/tex] < 3.00) - P([tex]\bar X[/tex] [tex]\leq[/tex] 2.68)
P([tex]\bar X[/tex] < 3.00) = P( [tex]\frac{\bar X-\mu}{\frac{\sigma}{\sqrt{n} } }[/tex] < [tex]\frac{3.00-2.68}{\frac{0.92}{\sqrt{25} } }[/tex] ) = P(Z < 1.74) = 0.9591
P([tex]\bar X[/tex] [tex]\leq[/tex] 2.68) = P( [tex]\frac{\bar X-\mu}{\frac{\sigma}{\sqrt{n} } }[/tex] [tex]\leq[/tex] [tex]\frac{2.68-2.68}{\frac{0.92}{\sqrt{25} } }[/tex] ) = P(Z [tex]\leq[/tex] 0) = 0.50
The above probability is calculated by looking at the value of x = 1.74 and x = 0 in the z table which has an area of 0.9591 and 0.50.
Therefore, P(2.68 < [tex]\bar X[/tex] < 3.00) = 0.9591 - 0.50 = 0.4591.
(b) Now, we have to find a sample size that would ensure that the first probability in part (a) is at least 0.99, that is;
P([tex]\bar X[/tex] [tex]\leq[/tex] 3.00) [tex]\geq[/tex] 0.99
P( [tex]\frac{\bar X-\mu}{\frac{\sigma}{\sqrt{n} } }[/tex] [tex]\leq[/tex] [tex]\frac{3.00-2.68}{\frac{0.92}{\sqrt{n} } }[/tex] ) [tex]\geq[/tex] 0.99
P(Z [tex]\leq[/tex] [tex]\frac{3.00-2.68}{\frac{0.92}{\sqrt{n} } }[/tex] ) [tex]\geq[/tex] 0.99
Now, in the z table; the critical value of x which has an area of at least 0.99 is given by 2.3263, that is;
[tex]\frac{3.00-2.68}{\frac{0.92}{\sqrt{n} } }=2.3263[/tex]
[tex]\sqrt{n} } }=\frac{ 2.3263\times 0.92}{0.32}[/tex]
[tex]\sqrt{n} } }=6.69[/tex]
n = 44.76 ≈ 45 {By squaring both sides}
Hence, the sample size must be 45 large enough that would ensure that the first probability in part (a) is at least 0.99.