Answer:
I came up with the answer check my questions to see it
Step-by-step explanation:
find the Perimeter Of a circle whose radius is 14cm
Answer:
88 cm
Step-by-step explanation:
Perimeter = 2πr
=2(14)(22/7)
= 88 cm
Answer:
87.97cm
Step-by-step explanation:
This question is asking to solve for the circumference.
The formula for the circumference of a circle is: [tex]\pi*diameter[/tex]
To work this out you would first need to multiply the radius of 14 by 2, this gives you 28cm. This is because the radius is half of the diameter.
The final step is to multiply pi by the diameter of 28, this gives you 87.97cm (87.9645943). This is because the formula for the circumference of a circle is [tex]\pi * diameter[/tex].
1) Multiply 14 by 2.
[tex]14*2=28[/tex]
2) Multiply pi by the diameter.
[tex]\pi*28^2=87.97 cm[/tex]
Select the correct answer. The velocity of a train relative to the ground is represented by the distance from A to B in the diagram. The velocity of a ball thrown inside the train at an angle of 66° relative to the train is represented by the distance from B to C. What is the distance from A to C (the velocity of the ball relative to the ground), correct to two decimal places? Assume that all the points in the diagram lie in the same plane. A. 21.14 m/s B. 18.03 m/s C. 17.20 m/s D. 15.00 m/s
Answer:
Step-by-step explanation:
we use cosine formula
2×15×10×cos(180-66)=15²+10²-AC²
-300 cos 66=225+100-AC²
AC²=325+300 cos 66
[tex]AC=\sqrt{325+300 cos 66} \approx 21.14 ~m/s[/tex]
The distance from A to C is 21.14. The correct option is A.
What is trigonometry?Trigonometry is the branch of mathematics which set up a relationship between the sides and angles of right-angle triangles.
Velocity is defined as the ratio of the distance moved by the object at a particular time. The velocity is a vector quantity so it needs both the magnitude and the direction.
Given that the velocity of a train relative to the ground is represented by the distance from A to B in the diagram. The velocity of a ball thrown inside the train at an angle of 66° relative to the train is represented by the distance from B to C.
The distance A to C will be calculated as,
2×15×10×cos(180-66)=15²+10²-AC²
-300 cos 66=225+100-AC²
AC=√(325+300 cos 66)
AC = 21.17 m/s
Therefore, the distance from A to C is 21.14. The correct option is A.
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Cody is a lifeguard and spots a drowning child 40 meters along the shore and 70 meters from the shore to the child. Cody runs along the shore for a while and then jumps into the water and swims from there directly to the child. Cody can run at a rate of 4 meters per second and swim at a rate of 1.1 meters per second. How far along the shore should Cody run before jumping into the water in order to save the child? Round your answer to three decimal places.
Answer:
Cody should run approximately 19.978 meters along the shore before jumping into the water in order to save the child.Thus,
Step-by-step explanation:
Consider the diagram below.
In this case we need to minimize the time it takes Cody to save the child.
Total time to save the child (T) = Time taken along the shore (A) + Time taken from the shore (B)
The formula to compute time is:
[tex]time=\frac{distance}{speed}[/tex]
Compute the time taken along the shore as follows:
[tex]A=\frac{x}{4}[/tex]
Compute the time taken from the shore as follows:
[tex]B=\frac{\sqrt{70^{2}+(40-x)^{2}}}{1.1}[/tex]
Then the total time taken to save the child is:
[tex]T=\frac{x}{4}+\frac{\sqrt{70^{2}+(40-x)^{2}}}{1.1}[/tex]
Differentiate T with respect to x as follows:
[tex]\frac{dT}{dx}=\frac{d}{dx}[\frac{x}{4}]+\frac{d}{dx}[\frac{\sqrt{70^{2}+(40-x)^{2}}}{1.1}][/tex]
[tex]=\frac{1}{4}-\frac{1}{1.1}\cdot \frac{(40-x)}{\sqrt{70^{2}+(40-x)^{2}}}[/tex]
Equate the derivative to 0 to compute the value of x as follows:
[tex]\frac{dT}{dx}=0[/tex]
[tex]\frac{1}{4}-\frac{1}{1.1}\cdot \frac{(40-x)}{\sqrt{70^{2}+(40-x)^{2}}}=0\\\\\frac{1}{1.1}\cdot \frac{(40-x)}{\sqrt{70^{2}+(40-x)^{2}}}=\frac{1}{4}\\\\4\cdot (40-x)=1.1\cdot [\sqrt{70^{2}+(40-x)^{2}}]\\\\\{4\cdot (40-x)\}^{2}=\{1.1\cdot [\sqrt{70^{2}+(40-x)^{2}}]\}^{2}\\\\16\cdot (40-x)^{2}=1.21\cdot [70^{2}+(40-x)^{2}}]\\\\16\cdot (40-x)^{2}-1.21\cdot (40-x)^{2}=5929\\\\14.79\cdot (40-x)^{2}=5929\\\\(40-x)^{2}=400.88\\\\40-x\approx 20.022\\\\x\approx 40-20.022\\\\x\approx 19.978[/tex]
Thus, Cody should run approximately 19.978 meters along the shore before jumping into the water in order to save the child.
The axis of symmetry for a quadratic equation can be found using the formula x equals StartFraction negative b Over 2 a EndFraction, where a and b are coefficients in the quadratic equation and x represents the values along a vertical line on the coordinate plane. What is the equation when solved for a?
Answer:
[tex]a=-\frac{b}{2x}[/tex]
Step-by-step explanation:
The equation of a quadratic function is given as:
ax² + bx + c = 0
where a, b and c are the coefficient in the quadratic equation.
The axis of symmetry of the quadratic equation is given as:
[tex]x=-\frac{b}{2a}[/tex]
To get the equation for a, we have to make a the subject of formula:
[tex]x=-\frac{b}{2a}\\\\multiply\ both\ sides\ by \ 2a:\\\\x*2a=-\frac{b}{2a}*2a\\\\2ax=-b\\\\Divide\ through\ by\ 2a\\\\2ax/2a=-b/2a\\\\a=-\frac{b}{2x}[/tex]
The value of a when solved from x = -b/2a is;
a = -b/2x
We are given the formula for axis of symmetry of a quadratic equation to be;
x = -b/2a
Where;
a and b are coefficients in the quadratic equation
x represents the values along a vertical line on the coordinate plane.
Now, we want to solve for a which means we make it the subject of the equation;
Using multiplication property of equality, we multiply both sides by 2a to get;
2ax = -b
We now use division property of equality by dividing both sides by 2x to get;
a = -b/2x
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Archer receives a day's work of pay, p, for 5 days of mowing lawns. He spent half of his money on gas. Then he spent $5 on water. Now, he has $40 left. Which equation represents how much Archer would get paid each day of mowing lawns?
Answer:
Daily pay= $18
5 days pay = $90
Step-by-step explanation:
Archer's daily pay =p
Pay for 5 days= 5p
Gas = 1/2 of 5p
= 1/2 × 5p
= 5p/2
Water = $5
Balance = $40
5p = 5/2p + 5 + 40
5p - 5/2p = 45
10p -5p /2 = 45
5/2p = 45
p= 45÷ 5/2
= 45 × 2/5
= 90/5
P= $18
5p= 5 × $18
=$90
The equation to determine Archer's daily pay is
5p = 5/2p + 5 + 40
Divide both sides by 5
p = 5/2p + 45 ÷ 5
= (5/2p + 45) / 5
p= (5/2p + 45) / 5
1 liter of ink can print 5000 pages of text. If you had 100 gallons of ink then how many pages could you print?
Answer:
500,000 pages
Step-by-step explanation:
1 / 5000 = 100 / x
x = 5000(100)
x = 500,000
Answer:
1892705 pages of text.
Step-by-step explanation:
g=Gallon
L=Liters
P=Pages
1L=5000p
1g=3.78541L
100g·3.78541L=378.541L
378.541L·5000=1892705
For a ,a relationship to be a function, which values cannot repeat: the x-
values or the y-values? *
Answer:
The x - valuesThe y-values repeat in various functions (for example: quadratic function: y=x²; y=4 for x=2 and for x=-2)
4:3=x:6, find the value of x please help me
Answer:
x=8
Step-by-step explanation:
4:3=x:6
Multiply the first set by 2
4*2 : 3*2
8:6
That means x =8
The polygons in each pair are similar. find the scale factor of the smallest figure to larger figure.
Greetings from Brasil...
It is said that polygons are similar, so we can use the expression of similarity.
BIG/small = BIG/small
35/14 = 25/X
X = 10
But the scale factor is questioned. Just use one of the expressions. We conclude that the largest is 2.5 times the value of the smallest
35/14 OR 40/16 OR 25/10
We get 2.5x-----------------------------------------------------------
BIG/small = BIG/small
25/5 = 40/Y
Y = 8
25/5 OR 25/5 OR 40/8
We get 5xtimes the value of the smallest
At which times could rory phone have been plugged into the charger?select three options
Answer:
9hrs 11hrs 19hrs
Step-by-step explanation:
just took the quiz on edge 2020
Answer:
9 hours, 11 hours, 19 hours.
The Fairy Tale Spectacular is coming to town. Admission to the fair costs $32.50 and each ride costs $0.80. You have $50 to spend at the Fairy Tale Spectacular including admission. Write and solve an inequality to determine the maximum number of rides you can enjoy at the Fairy Tale Spectacular?
Answer:21
Step-by-step explanation:
50-32.5=17.5
17.5/0.8=21.875
What are the solutions to the equation 3(x – 4)(x + 5) = 0? x = –4 or x = 5 x = 3, x = 4, or x = –5 x = 3, x = –4, or x = 5 x = 4 or x = –5
Answer:
x= 4 x = -5
Step-by-step explanation:
3(x – 4)(x + 5) = 0
Using the zero product property
(x – 4)=0 (x + 5) = 0
x= 4 x = -5
What are the solutions to the equation 3(x – 4)(x + 5) = 0?
x = –4 or x = 5
x = 3, x = 4, or x = –5
x = 3, x = –4, or x = 5
x = 4 or x = –5
Answer:
D. x = 4 or x = –5
Step-by-step explanation:
What is the 6th row of Pascal's triangle?
Answer:
1, 6, 15, 20, 15, 6, 1
Mia’s average driving speed is 6 kilometers per hour faster than Kirk’s. In the same length of time it takes Mia to drive 558 kilometers, Kirk drives only 522 kilometers. What is Mia’s average speed?
Answer:
93km/hr
Step-by-step explanation:
Using the formula Speed = Distance/Time. From the formula we can substitute for time as shown;
Time = Distance/Speed
Let the distance and speed travelled by Mia be Dm ans Ds respectively
Distance travelled by Kirk be Km and and Ks respective.
Time taken be Mia to travel Tm = Dm/Sm
Time taken be Kirk to travel Tk = Dk/Sk
Since it takes the same length of time for both of them to travel, then Tm = Tk. Hence Dm/Sm = Dk/Sk
Given parameters
Dm = 558 kilometers
Dk = 522 kilometres
If Mia’s average driving speed is 6 kilometers per hour faster than Kirk’s, then Mia's driving speed Sm = 6 + Sk
Required
Mia’s average speed (Sm)
Since Dm/Sm = Dk/Sk
Substituting the given values to get Sk first we have;
558/6+Sk = 522/Sk
Cross multiply
558Sk = 522(6+Sk)
open the parenthesis
558Sk = 3132 + 522SK
558Sk-522Sk = 3312
36Sk =3132
Sk = 3132/36
Sk =87km/hr
SInce Sm = 6+Sk
Sm = 6+87
Sm = 93km/hr
Hence Mia's average speed is 93km/hr
solution for 2x is equal to 10
Answer:
The answer is 5
Step-by-step explanation:
divide 10 by two and get 5
Answer:
[tex]x = 5[/tex]
Step-by-step explanation:
We have the equation [tex]2x = 10[/tex], we can try and isolate x by dividing both sides by 2.
[tex]2x \div 2 = 10\div2\\x = 5[/tex]
Hope this helped!
Sandra spotted the sailboat from the shore and measured the angle from the waterline to the top of the boats mast to be 7° if the top of the mask is 23 feet above the water how far is the middle of the sailboat from the shore? Estimate your answer to the nearest tenth.
Answer:
The middle of the sailboat is approximately 268.8 feet from the shore.
Step-by-step explanation:
Let the distance from shore to the middle of the boat be represented by x, the angle of elevation of Sandra from the shore to the top of the boat mast is 7°. Applying the required trigonometric function to this question, we have;
Tan θ = [tex]\frac{opposite}{adjacent}[/tex]
Tan 7° = [tex]\frac{23}{x}[/tex]
⇒ x = [tex]\frac{23}{Tan 7^{0} }[/tex]
= [tex]\frac{23}{0.12279}[/tex]
= 268.7515
∴ x = 268.8 feet
The middle of the sailboat is approximately 268.8 feet from the shore.
Complex numbers
[ = square root symbol
-[-64
How would I find this?
[tex]-\sqrt{-64}=-\sqrt{8^2\cdot (-1)}-8\sqrt{-1}=-8i[/tex]
Newly planted seedlings approximately double their weight every week. If a seedling weighing 5 grams is planted at time t=0 weeks, which equation best describes its weight, W, during the first few weeks of its life?
Answer:
[tex]W(t)=5(2^t)[/tex]
Step-by-step explanation:
Given that the Newly planted seedlings approximately double their weight every week and a seedling weighing 5 grams is planted at time t = 0 weeks. This represent an exponential function with an equation in the form:
[tex]W(t)=ab^t[/tex].
W(t) is the weight in t weeks, t is the weeks and a is the weight when t = 0. At t = 0, W = 5 g:
[tex]W(t)=ab^t\\W(0)=ab^0\\5=ab^0\\a=5[/tex]
Since the weight double every week, b = 2. The exponential function is given as:
[tex]W(t)=ab^t\\\\W(t)=5(2^t)[/tex]
Ernesto solves the equation below by first squaring both sides of the equation. \sqrt{\dfrac{1}{2}w+8}=-2 2 1 w+8 =−2square root of, start fraction, 1, divided by, 2, end fraction, w, plus, 8, end square root, equals, minus, 2 What extraneous solution does Ernesto obtain?
Answer:
w = -8Step-by-step explanation:
Given the equation solved by Ernesto expressed as [tex]\sqrt{\dfrac{1}{2}w+8}=-2[/tex], the extraneous solution obtained by Ernesto is shown below;
[tex]\sqrt{\dfrac{1}{2}w+8}=-2\\\\square\ both \ sides \ of \ the \ equation\\(\sqrt{\dfrac{1}{2}w+8})^2=(-2)^2\\\\\dfrac{1}{2}w+8 = 4\\\\Subtract \ 8 \ from \ both \ sides\\\\\dfrac{1}{2}w+8 - 8= 4- 8\\\\\dfrac{1}{2}w= -4\\\\multiply \ both \ sides \ by \ 2\\\\\dfrac{1}{2}w*2= -4*2\\\\w = -8[/tex]
Hence, the extraneous solution that Ernesto obtained is w = -8
Which of the following best describes the graph shown below?
16
A1
1
14
O A This is the graph of a linear function
B. This is the graph of a one-to-one function
C. This is the graph of a function, but it is not one to one
D. This is not the graph of a function
The vertical line test helps us see that we have a function. Note how it is not possible to draw a single straight line through more than one point on the curve. Any x input leads to exactly one y output. This graph passes the vertical line test. Therefore it is a function.
The function is not one-to-one because the graph fails the horizontal line test. Here it is possible to draw a single straight horizontal line through more than one point on the curve. The horizontal line through y = 2 is one example of many where the graph fails the horizontal line test, meaning the function is not one-to-one.
The term "one-to-one" means that each y value only pairs up with one x value. Here we have something like y = 2 pair up with multiple x values at the same time. This concept is useful when it comes to determining inverse functions.
Will has 2 quarters, 6 dimes, some nickels, and 4 pennies. If the ratio of pennies to the total number of coins he has is 1:5, how many nickels are there?
Answer:
8 nickels
Step-by-step explanation:
Let n be the number of nickels.
4: (2+ 6 + 4 + n) = 1:5
4÷(12 + n) = 1÷5
4 x 5 = 1 x (12 + n)
20 = 12 + n
n = 8
A model of a wedge of cheese is used in a display for a deli. All the sides of the model are covered in yellow construction paper. A rectangular prism has a rectangular base with length of 15 centimeters and height of 5 centimeters. Another rectangle has length of 15 centimeters and height of 13 centimeters. Another rectangle has length of 15 centimeters, and height of 12 centimeters. The triangular sides have a base of 5 centimeters and heights of 12 centimeters. How much construction paper is needed for the model? 45 square cm 330 square cm 510 square cm 570 square cm
Answer:
510 cm²
Step-by-step explanation:
To find how much construction paper is needed for the model, we calculate the total areas of each of its sides.
The area of the first triangular sides is A₁ = 15 cm × 5 cm = 75 cm²
The area of the second triangular sides is A₂ = 15 cm × 13 cm = 195 cm²
The area of the third triangular sides is A₃ = 15 cm × 12 cm = 180 cm²
The area of each triangular side is A₄ = 1/2 × 5 cm × 12 cm = 30 cm²
The area of the two triangular sides is A₅ = 2A₄ = 2 × 30 cm² = 60 cm²
The total surface area of a wedge of cheese is A = A₁ + A₂ + A₃ + A₅ = 75 cm² + 195 cm² + 180 cm² + 60 cm² = 510 cm²
So the amount of construction paper needed equals the total surface area of the wedge of cheese = 510 cm²
Answer:
510
Step-by-step explanation:
A 250.0 kg rock falls off a 40.0 m cliff. What is the kinetic energy of the rock just before it hits the ground (hint: conservation of energy)?
Answer:
kinetic energy body when it hits the ground is 98000 joule
1000joule = 1 kilojoule
, kinetic energy body when it hits the ground is 98 kilo-joule
Step-by-step explanation:
conservation of energy states that total energy of a system remains constant.
Potential energy of body = mgh
m = mass
g = gravitational pull = 9/8 m/s^2
h = height
kinetic energy = 1/2 mv^2
where v is the velocity of body
________________________________________
Total energy for this at any point is sum of potential energy and kinetic energy
total energy at height h
v= 0
PE = 250*9.8*40= 98,000
KE = 1/2 m0^2 = 0
total energy at when ball hits the ground
h=0
PE = 250*9.8*0 =
KE = 1/2 mv^2
_______________________________________\
Applying conservation of energy
Total energy at height h = total energy at ground
98000 = KE
Thus, kinetic energy body when it hits the ground is 98000 joule
1000joule = 1 kilojoule
, kinetic energy body when it hits the ground is 98 kilo-joule
What are the domain and range of the real-valued function f(x)=2/(x+5)?
Answer:
Domain is all real numbers, x ≠ -5
Range is all real numbers, y ≠ 0
Step-by-step explanation:
Compute the range and interquartile range for the data collected for boys and girls. Describe their differences in detail using specific terms of spread. (4 points)
Answer:
The measure of central tendency, mean and median are approximately equal for the boys indicating that the data of the boys is more evenly spread while standard deviation of the girls data is less than those of the boys indicating that the data for the girls is less widely spread.
Step-by-step explanation:
The given data are;
, 1 2 3 4 5 6 7 8 9 10
Girls, 50 32 15 56 81 50 18 81 22 55
Boys, 75 41 25 22 7 0 43 12 45 70
Sorting the data gives;
Girls, 15, 18, 22, 32, 50, 50, 55, 56, 81, 81
Boys, 0, 7, 12, 22, 25, 41, 43, 45, 70, 75
For the even numbered sample data size, the first quartile, Q₁ is found by sharing the data into two and finding the median of the left half which gives;
10/2 = 5 on each half
The first quartile, Q₁, is the median of the left 5 data points which is the 3rd data point = 22 for girls and 12 for boys
The third quartile, Q₃, is found in similar method to be the 8th data point which is 56 for girls and 45 for boys
The median = 50 for girls and 33 for boys
Therefore, the interquartile ranges are;
IQR = 56 - 22 = 34 for girls, 45 - 12 = 33 for boys
We check for outliers.
Q₁ - 1.5×IQR = 22 - 1.5*34 = -29
Q₃ + 1.5×IQR = 56 + 1.5*34 = 107
We check the mean of both data samples as follows;
Average for the girls = 46
Average for the boys = 34
Standard deviation for girls = 23.99
Standard deviation for girls = 25.43
Therefore, the measure of central tendency is more accurate for the boys indicating that the data of the boys is more evenly spread while the data for the girls is less widely spread.
What is the formula for finding mean or average?
Answer:
LOOK BELOW
Step-by-step explanation:
I would not call the explanation a formula
All you have to do to solve mean or average is add all of the numbers up and divide by the total amount of numbers
so for example
0,2,4,0,2,3,2,8,6 <-------- lets find the mean/average
0+2+4+2+3+2+8+6= 27/amount of numbers
amount of numbers=9
(count the zeros too!)
27/9=3
3 is the mean or average!!!
what's the square footage of 12'3" * 18'4"
Answer:
multiply length time width
Meguel does not understand which digit is in the tenths location in the number 514.196 Where would it be located at
Answer:
first number after the decimal point
Step-by-step explanation:
after the decimal point is the tenths, hundredths, and thousandths place.
0.1 - tenths
0.09 - hundredths
0.006 - thousandths
The point-slope form of the equation of the line that passes through points (-5,-1) and (10, -7 ) is y-4=1/4 (x-8) what is the slope intercept form of the equation for this line ?
Answer:
y = [tex]\frac{1}{4}[/tex] x + 2
Step-by-step explanation:
The equation of a line in slope- intercept form is
y = mx + c ( m is the slope and c the y- intercept )
Given
y - 4 = [tex]\frac{1}{4}[/tex] (x - 8) ← distribute
y - 4 = [tex]\frac{1}4}[/tex] x - 2 ( add 4 to both sides )
y = [tex]\frac{1}{4}[/tex] x + 2 ← in slope- intercept form
The body paint, an automobile body paint shop, has determined that the painting time of automobiles is uniformly distributed and that the required time ranges between 45 minutes to 11/2hours.
What is the probability that the painting time will be less than or equal to an hour?
What is the probability that the painting time will be more than 50 minutes?
Determine the expected painting time and its standard deviation.
Answer:
a. [tex]\mathbf{P(Y \leq 60) = 0.3333}[/tex]
b. P(Y>50) = 0.8889
c. E(y) = 67.5 and Standard deviation [tex]\sigma[/tex] = 12.99
Step-by-step explanation:
From the information given :
an automobile body paint shop, has determined that the painting time of automobiles is uniformly distributed and that the required time ranges between 45 minutes to [tex]1\frac{1}{2}[/tex]hours.
The objective is to determine the probability that the painting time will be less than or equal to an hour?
since 60 minutes make an hour;
[tex]1\frac{1}{2}[/tex]hours = 60 +30 minutes = 90 minutes
Let Y be the painting time of the automobile; then,
the probability that the painting time will be less than or equal to an hour ca be computed as :
[tex]P(Y \leq 60) = \int ^{60}_{45} f(y) dy \\ \\ \\ P(Y \leq 60) = \int ^{60}_{45} \dfrac{1}{45} dy \\ \\ \\ P(Y \leq 60) = \dfrac{1}{45} \begin {pmatrix} x\end {pmatrix}^{60}_{45} \\ \\ \\ P(Y \leq 60) = \dfrac{60-45}{45 } \\ \\ \\ P(Y \leq 60) = \dfrac{15}{45} \\ \\ \\ P(Y \leq 60) = \dfrac{1}{3} \\ \\ \\ P(Y \leq 60) = 0.3333[/tex]
What is the probability that the painting time will be more than 50 minutes?
The probability that the painting will be more than 50 minutes is P(Y>50)
So;
[tex]P(Y>50) = \int \limits ^{90}_{50} f(y) dy[/tex]
[tex]P(Y>50) = \int \limits ^{90}_{50} \dfrac {1}{45} dy[/tex]
[tex]P(Y>50) = \dfrac{1}{45}[x]^{90}_{50}[/tex]
[tex]P(Y>50) = (\dfrac{90-50}{45})[/tex]
[tex]P(Y>50) = \dfrac{40}{45}[/tex]
P(Y>50) = 0.8889
Determine the expected painting time and its standard deviation.
Let consider E to be the expected painting time
Then :
[tex]E(y) = \int \limits ^{90}_{45} y f(y) dy \\ \\ \\ E(y) = \int \limits ^{90}_{45} y \dfrac{1}{45} dy \\ \\ \\ E(y) = \dfrac{1}{45} [\dfrac{y^2}{2}]^{90}_{45} \\ \\ \\ E(y) = \dfrac{1}{45}[\dfrac{(90^2-45^2)}{2}] \\ \\ \\ E(y) = \dfrac{1}{45} (\dfrac{6075}{2}) \\ \\ \\ E(y) = \dfrac{1}{45} \times 3037.8 \\ \\ \\ \mathbf{E(y) = 67.5}[/tex]
[tex]E(y^2) = \int \limits ^{90}_{45} y^2 f(y) dy \\ \\ \\ E(y^2) = \int \limits ^{90}_{45} y^2 \dfrac{1}{45} dy \\ \\ \\ E(y^2) = \dfrac{1}{45} [\dfrac{y^3}{3}]^{90}_{45} \\ \\ \\ E(y^2) = \dfrac{1}{45}[\dfrac{(90^3-45^3)}{3}] \\ \\ \\ E(y^2) = \dfrac{1}{45} (\dfrac{637875}{3}) \\ \\ \\ E(y^2) = \dfrac{1}{45} \times 2126.25 \\ \\ \\ \mathbf{E(y^2) = 4725}[/tex]
To determine the standard deviation, we need to first know what is the value of our variance,
So:
Variance [tex]\sigma^2[/tex] = E(x²) - [E(x)]²
Variance [tex]\sigma^2[/tex] = 4725 - (67.5)²
Variance [tex]\sigma^2[/tex] = 4725 - 4556.25
Variance [tex]\sigma^2[/tex] = 168.75
Standard deviation [tex]\sigma[/tex] = [tex]\sqrt{variance}[/tex]
Standard deviation [tex]\sigma[/tex] = [tex]\sqrt{168.75}[/tex]
Standard deviation [tex]\sigma[/tex] = 12.99
