A woman has eight keys on a key ring, one of which fits the door she wants to unlock. Sherandomly selects a key and tries it. If it does not unlock the door, she randomly selects anotherkey from those remaining and tries to unlock the door with it. She continues in this manner untilthe door is unlocked. Let X be the number of keys she tries before unlocking the door, countingthe key that actually worked.

Required:
Find the expected number of keys she will try before she opens the door.

Answers

Answer 1

Answer:

The expected number of keys she will try before she opens the door is 4.5.

Step-by-step explanation:

A woman has eight keys on a key ring, one of which fits the door she wants to unlock.

Each of them is equally as likely to be the one to work, which means that this situation is represented by an uniform distribution with lower bound [tex]a = 1[/tex] and upper bound [tex]b = 8[/tex].

Find the expected number of keys she will try before she opens the door.

The expected value of the uniform distribution is given by:

[tex]E = \frac{a + b}{2}[/tex]

Considering [tex]a = 1, b = 8[/tex], as is the case in this exercise:

[tex]E = \frac{1 + 8}{2} = 4.5[/tex]

The expected number of keys she will try before she opens the door is 4.5.


Related Questions

What is the area of this quadrilateral?
2 ft
4 ft
6 ft
6 ft
4 ft
2 ft
A. 28 square feet
0
B. 48 square feet
a o
C. 18 square feet
D. 36 square feet

Answers

Answer:

the answer would be a

Step-by-step explanation:

Answer:

36

Step-by-step explanation:

just got it correct

Um gato come 5 ratos por dia. Quantos ratos 5 gatos comem em 5dias?​

Answers

Answer:

1 gato come 5 ratos em 1 dia X 5 = 5 gatos come 25 ratos por dia

5 gatos come 25 ratos por dia X 5 = 25 gatos come 125 ratos por dia

5 and 1/4 - 4 and 1/2​

Answers

This answer is 0.75 , hope this helps ❤️.

Step-by-step explanation:

answer: 3/4 or 0.75

=5 1/4 - 4 1/2

=21/4 - 9/2

= (21-9) / 4

=3/4  or 0.75

Hi I'm bad at math the questions is -r - 20r = please help

Answers

Answer:

−21r

Step-by-step explanation:

Combine Like Terms:

=−r+−20r

=(−r+−20r)

=−21r

Answer:

=−21r

please click the crown button (brainliest) thanks!!

hope this helps!! <3

-21r. Hope this helps

what is the volume of a sphere if the radius is 9?


ANSWER IN TERMS OF PI !!!

Answers

Volume of sphere =4/3 pi r^3
V(volume)=(3/4) pi r
Pi =3.14 or 22/7
R(r)= radius (9) in

In a nutshell :

The volume of a sphere is equal to 43 times Pi π times the radius cubed. Substitute the value of the radius r=9 into the formula to find the volume of the sphere. Pi π is approximately equal to 3.14 .

9 - x < - 11
Show steps please

Answers

Answer: x > 20

Step-by-step explanation:

9 - x < - 11

In this scenario, we've to collect like terms in order to.wolve for x. This will be:

9 - x < - 11

- x < - 11 - 9

- x < - 20

Divide both side by -1

-x/-1 < -20/-1

When we divide by a coefficient with minus sign, the sign changes too from less than to greater than

-x/-1 < -20/-1

x > 20

Select all the statements about rotations that are true

A- The shapes of the figure does not change.

B- The positions of the figure does not change.

C- The size of the figure does not change.

D- The orientation of the figure does not change.

E- The coordinates of the figure do not change.

Please help I will give 100 points

Answers

Answer:

a. true

b. false

c. false

d. true

e. false

Step-by-step explanation:

A. true, a shape is not warped by a rotation

b. false, the points on the figure will change

c. false, the size is not affected by a rotation

d. true, the orientation changes in a rotation

e. false, the coordinate points on the figure are altered

Answer:

A- The shapes of the figure does not change.

C- The size of the figure does not change.

D- The orientation of the figure does not change

Write 11 k-6 (2k+5)in expanded form and find the sum

Answers

Answer:

Option B

Step-by-step explanation:

Expression representing the series is,

[tex]\sum_{k=6}^{11}(2k+5)[/tex]

Here, k = Number of terms

By placing k = 6, 7, 8, 9, 10, 11 in the expression we can get the terms of the series.

For k = 6,

(2k + 5) = 2(6) + 5

            = 17

For k = 7,

(2k + 5) = 2(7) + 5

             = 19

For k = 8,

(2k + 5) = 2(8) + 5

            = 21

For k = 9,

(2k + 5) = 2(9) + 5

            = 23

For k = 10,

0(2k + 5) = 2(10) + 5

            = 25

For k = 11,

(2k + 5) = 2(11) + 5

            = 27

Therefore, expanded form will be,

17, 19, 21, 23, 25, 27

There, is a common difference in each successive to previous term,

d = 19 - 17

d = 2

Number of terms 'n' = 6

First term = 17

Sum of an arithmetic sequence is given by,

[tex]S=\frac{n}{2}[2a+(n-1)d][/tex]

Therefore, sum of the given sequence will be,

[tex]S=\frac{6}{2}[2(17)+(6-1)2][/tex]

   = 3(34 + 10)

S = 132

Option B will be the correct option.


The estimated difference of 3209 and 1893, when rounded off to the nearest ten is
o(a) 1300
(b) 1310
(c) 1320
0 (d) 1000

Answers

Answer:

[tex] = (3209) - (1893) \\ = 1.32 \times {10}^{3} \\ = 1320[/tex]

[tex] \small{ \star{ \underline{ \blue{becker}}}}[/tex]

Answer:

1320

Step-by-step explanation:

round off

3209 ≈ 3210

1893 ≈ 1890

estimated difference = 3210 - 1890 = 1320

A pinwheel's four blades are all congruent right trapezoids.

4 in

2 in

2 in

What is the combined area of the four blades, in square inches?

Answers

Answer:

[tex]Area = 24\ in^2[/tex]

Step-by-step explanation:

Given

Let

[tex]a, b \to[/tex] opposite sides of each trapezoid

[tex]h \to[/tex] height

[tex]a = 2; \ \ \ b = 4 \ \ \ \ h = 2[/tex]

See attachment for trapezoids

Required

The combined area of the 4

First, we calculate the area of 1

[tex]Area = \frac{1}{2}(a + b) * h[/tex]

So:

[tex]A_1 = \frac{1}{2}(2 + 4) * 2[/tex]

[tex]A_1 = \frac{1}{2}*6 * 2[/tex]

Using a calculator

[tex]A_1 = 6[/tex]

The combined area is:

[tex]Area =n * A_1[/tex]

Where

[tex]n = 4[/tex] --- 4 blades

So:

[tex]Area = 4 * 6[/tex]

[tex]Area = 24\ in^2[/tex]

If the square of a positive integer is added to four times to integer the result is 117 find the integer.

Answers

Answer:

x = -2 ± 452i

Step-by-step explanation:

x² + 4x = 117

x² + 4x - 117 = 0

if you solve this quadratic by using the quadratic formula you get:

x = -2 ± 452i

452i is an imaginary number that equals [tex]\sqrt{-452}[/tex]

please help will mark brainlist!!​

Answers

Answer:

x=28

y=28

Step-by-step explanation:

Equation 1:

Dived both sides by 0.75 to remove 3/4 from x.

(x-12)=16

Now, add 12 to both sides.

x=28

Equation 2:

Same here, divide both sides by 0.75.

y-12=16

Add 12 to both sides.

y=28

Alex collects coins that appreciate (increase in) value. At the store he has found three coins that he likes and can afford. Help Alex decide which coin to buy by selecting two coins and comparing their values over time. 1. Which two coins are you going to compare? Circle the two coins you picked. Coin A Coin B Coin C Finding Equations for the Values 2. What are the current values and appreciation rates of the two coins you selected? (2 points: 1 point for each of 2 coins) Coin Current Value Annual Appreciation Rate 3. Write an exponential equation for each coin that will give the coin's value, V, at any time, t. Use the formula: V(t) = P(1 + r)t, where V(t) is the value of the coin in t years, P is the initial investment, and r is the growth rate. For each of the coins you selected, identify P and r, then set up an equation to find the value of the coin at any t. (2 points: 1 point for each coin) Coin P r Function V(t) = V(t) = Interpreting Exponential Expressions 4. In the coin value formula, V(t) = P(1 + r)t, which part(s) form the base of the exponential function? Which part(s) form the constant, or initial value? Which part(s) form the exponent? (4 points: 1 point for each answer below) Base: Constant, or initial value: Exponent: In this function, if the value of r were to increase, would the value represented by P also increase or stay the same? Why? Explain your answer using terms such as "rate of growth" and "initial value" in the context of the coin problem. 5. Find the value of the coins after 10, 20, 30, and 60 years. Use the function you identified in question 3 to calculate the value. (8 points: 1 point for each time interval) Coin A Coin B Coin C Initial Value 10 years 20 years 30 years 60 years Determining the More Valuable Coin 6. Which coin is more valuable after 10 years? 20 years? 30 years? 60 years? Which coin would you purchase if you intended to keep it longer than 60 years, and why? (Hint: Loo

Answers

Answer:

Coin A:

10:$46.18

20:$96.74

30:$190.31

60:$1448.66

Coin B

10:$65.16

20:$106.13

30:$172.88

60:$466.98

Coin C

10:$88.81

20:$131.47

30:$194.60

60:$631.18

I think these are right. I've rounded the answers to the nearest 10th place.

will give brainliest and 50 points
Given the inequality -8 < 2, explain what happens when you multiply or divide both sides by 2 and what happens when you multiply or divide both sides by -2.

Answers

when you divide -8/2=-4 and 2/2=1

-4<1

when you divide by a negative number your sign changes

4>-1

When you multiply or divide each side by 2, the signs stay the same. −16 < 4 and −4 < 1. When you multiply or divide by −2, the inequality sign reverses. 16 > −4 and 4 > −1.

Answer:

see below

Step-by-step explanation:

When multiplying or dividing an inequality by a positive, the inequality remains the same direction

3x < 6

Divide by 3

3x/3 < 6/3

x <2

When multiplying or dividing an inequality by a negative, the inequality changes direction

-3x < 6

-3x/ -3 > 6/-3

x > -2

quickly help 1//////////////////////////////////

Answers

Answer:

1 [tex]\frac{2}{8}[/tex]

Step-by-step explanation:

The largest is 1 [tex]\frac{4}{8}[/tex], and the smallest is [tex]\frac{2}{8}[/tex]. 1 [tex]\frac{4}{8}[/tex] - [tex]\frac{2}{8}[/tex] = 1 [tex]\frac{2}{8}[/tex].

Solve the equation
X/x+2 - 4/x-2=1​

Answers

Answer: - 2/3 but in decimal form it is -0.6 repeating

Step-by-step explanation:

The point-slope form of the equation of the line that passes through (–4, –3) and (12, 1) is y – 1 = y minus 1 equals StartFraction one-fourth EndFraction left-parenthesis x minus 12 right-parenthesis.(x – 12). What is the standard form of the equation for this line?

Answers

Given:

The line passes through the two points (–4, –3) and (12, 1).

The point-slope form of the equation of the line is:

[tex]y-1=\dfrac{1}{4}(x-12)[/tex]

To find:

The standard form of the equation for this line.

Solution:

The standard form of a line:

[tex]Ax+By=C[/tex]

The given point-slope form of the equation of the line is:

[tex]y-1=\dfrac{1}{4}(x-12)[/tex]

Multiply both sides by 4.

[tex]4(y-1)=(x-12)[/tex]

[tex]4y-4=x-12[/tex]

[tex]-4+12=x-4y[/tex]

[tex]8=x-4y[/tex]

Interchanging the sides, we get

[tex]x-4y=8[/tex]

Therefore, the standard form of the equation for this line is [tex]x-4y=8[/tex].

y = one-fourth x minus three-fourths got it on the edge

\-x+sqrt1−x
2
\-=sqrt2(2x
2
−1)

Answers

Answer:

3sqrt2

Step-by-step explanation:

b jhf vj fjvfd vmnd fmv ndkfv mndfvdf nkvvdf lkv nf khlfd hjvdf

I need help with this question

Answers

Answer:

[tex]sin\theta = \frac{5}{14}\\\\\theta = sin^-1 \frac{5}{14}\\\\\theta = 20.9[/tex]

Option B: 20.9°

19 POINTS the answer is not the first or second option I’m maybe think the last one

Answers

D) there is almost no connection between US stocks and over seas stocks, since the US economy is different than the North Korean economy (the economy controls the stocks)

50 points!!!!! need answer ASAP

Answers

Answer:

the first option

Step-by-step explanation:

i believe

Mrs. Fox met with 120 students. If three- quarters were girls, how many boys were at the meeting

Answers

Answer:30 boys

Step-by-step explanation: There are 120 students, three-fourths are girls. Nine out of twelve is equal to three fourths, if you add a zero to the end of twelve and nine you get 90 out of 120, which is how many girls there are. If you subtract 90 from 120 you get 30 or one-fourth. The number of boys is equal to one-fourth because there is only one-foutlrth left. So, there are 30 boys.

explain why a3*a2 dosnt equal a6... Plz I need help!​

Answers

Answer: a^3 · a^2 ≠ a^6 as the laws of exponents states that the multiplication rule for two exponents with the same bases equates to addition, so that a^3 · a^2 = a^3+2 = a^5.

guys please help its my final either i pass or not

Answers

Answer:

Step-by-step explanation:

1 yes 2 no 3 no 4 yes 5 no

Answer:

1. yes

2. yes

3. no

4. yes

5. no

Step-by-step explanation:

go to mathwa* and type in the same equation and click to see if function or not.

gl on the final

this guy above me is wrong for #2

Pls help I’ll brainlest ASAP

Answers

Answer:

A) -1

Step-by-step explanation:

anything raised to the zero power is 1 but if there is a negative without parentheses around it then it becomes -1

ex, (-4)° = 1

Answer:

It would be -1.

Step-by-step explanation:

This is because any postive number to the power of 0 equals 1 but since there is a negative sign, it would become -1.

Hey Besties! Pls help! 50 pts!
Which is the graph of f(x) = one-fourth(4)x?

On a coordinate plane, an exponential function approaches y = 0 in quadrant 1. It curves up to the left and goes through points (2, 1) and (0, 4).

On a coordinate plane, an exponential function approaches y = 0 in quadrant 1. It curves up to the left and goes through points (1, 1) and (0, 4).

On a coordinate plane, an exponential function approaches y = 0 in quadrant 2 and goes through points (3, 2) and (4, 4).

On a coordinate plane, an exponential function approaches y = 0 in quadrant 2 and goes through points (1, 1) and (2, 4).

Answers

The graph of the function [tex]f(x) = \frac 14(4)^x[/tex] is (d) on a coordinate plane, an exponential function approaches y = 0 in quadrant 2 and goes through points (1, 1) and (2, 4).

What are functions?

Functions are used to represent equation, graphs and tables

The equation of the function is given as:

[tex]f(x) = \frac 14(4)^x[/tex]

The above function is an exponential function that has an initial value of 1/4 and a rate of 4

When x = 2,

f(2) = 4

When x = 1,

f(1) = 1

Hence, the graph of the function [tex]f(x) = \frac 14(4)^x[/tex] is (d)

Read more about exponential functions at:

https://brainly.com/question/11464095

Answer:

graph one

Step-by-step explanation:

did it on ed .

Can the surface area of a sphere and the volume of a sphere be the same numerical value if the units are measured relative to the same unit of length?
A. Yes; the radius would need to be the unit radius, 1.
B. Yes; the radius would need to be 3.
C. No, the surface area would always be greater than the volume.
D. No, the volume would always be greater than the surface area.

Answers

Answer:

Volume = surface area

[tex]\frac{4}{3}\pi r^3 = 4\pi r^2\\\\\frac{r}{3} = 1\\r = 3[/tex]

option B

Solve for X: -10+3X<4

Answers

Answer:

x<14/3

Step-by-step explanation:

-10+3x<4

3x<4+10

3x<14

x<14/3

If this helps please mark as brainliest

In ∆PQR, ∠P = 90degrees , PQ= 12 cm, PR=16cm. Find ∠Q

Answers

Answer:

∠Q  = 53.13 degrees

Step-by-step explanation:

Given that ∆PQR, ∠P = 90degrees , this means that the triangle is a right angled triangle

Hence using the notation

SOH CAH TOA

where S is sine, C is cosine, T is tangent and O, A and H represents the size of the opposite, adjacent and hypotenuse sides

Considering  ∠Q and the given sides

PR=16cm is the opposite side,

PQ= 12 cm is the adjacent side hence we use TOA

Tan Q = 16/12 =

Q = Arc tan 16/12

= 53.13 degrees

The matching section of an exam has 3 questions and 7 possible answers. In how many different ways can a student answer the 3 questions, if none of the answer choices can be repeated?
O combination
O permutation​

Answers

Answer:permutations

Step-by-step explanation:

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