1/2a+b+1/2a-b please solve it

The mean time it takes to walk to the bus stop is 8 minutes (with a standard deviation of 2 minutes) and the mean time it takes

kifflom [539]

We have been given for a normal distribution the mean time it takes to walk to the bus stop is 8 minutes with a standard deviation of 2 minutes. And the mean time it takes for the bus to get to school is 20 minutes with a standard deviation of 4 minutes.

(a) Average time that it would take reach school can be obtained by adding the average times.

8+20 = 28 minutes.

(b) Standard deviation of the trip to school can be found as:

$\sigma =\sqrt{2^{2}+4^{2}}=\sqrt{4+16}=\sqrt{20}=4.47$

Therefore, standard deviation of the entire trip is 4.47 minutes.

(c) Let us first find z score corresponding to 30 minutes. $z=\frac{x-\mu }{\sigma }=\frac{30-28}{4.47}=0.447$

We need to find the probability such that $P(x>30)=P(z>0.447)=0.67$

Therefore, the required probability is 0.67.

(d) If average time to walk to school is 10 minutes, then overall average time for the trip will be 10+20 = 30 minutes.

(e) Standard deviation won't change it will remain 4.47

(f) The new probability will be:

$z=\frac{x-\mu }{\sigma }=\frac{30-90}{4.47}=0$

$P(x>30)=P(z>0)=0.5$

Therefore, probability will be 0.50.

6 0

3 years ago

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Solve this system of linear equations. Separate

Tems11 [23]

Answer:

(-7,-4)

Step-by-step explanation:

There are 2 different ways to solve a system of equations and the one I'm going to show you will work for all systems. To start we will solve one of the equations for either X or Y it doesn't matter which one so I will choose the second one. Divide both sides by negative 4 and you will have the solved equation. x=1+2y Now we know what x equals so we can plug "1+2y" into the other equation where we see an X and we will get -8(1+2y)=24-8y and since we only have one variable now we can solve to get what Y is. The first step is distributing -8-16y=24-8y now lets put the Y's together on one side and the numbers together on the other -32=8y and just divide both sides by 8 to get the value of Y -4=y Now that we have Y we can plug -4 into either equation as Y to get the value of X I will use the second equation. -4x=-4-8(-4) and solve for X -4x=-4+32 -4x=28 x=-7 So now we have x and y and we can write it as out solution (-7, -4)

I hope this helps and please don't hesitate to ask if there is anything still unclear!

3 0

3 years ago

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Calculate the expected value, the variance, and the standard deviation of the given random variable X. (Round all answers to two

Tom [10]

Answer:

E (X) = 1.8

Var (X) = 0.36

σ = 0.6

Step-by-step explanation:

Solution:-

- Denote the random variable X : is the number of red marbles that Suzan has in her hand after she selects three marbles.

- Total sample space (bag) have the following quantity of colored marbles:

Bag : { 3 Red , 2 Green }

- Suzan selects three marbles from the bag. The Event (X) defines the number of red marbles out of 3.

- The total number of outcomes / selections for randomly selecting 3 balls from the bag:

All outcomes = 5 C 3 = 10

- The probability distribution of the random variable X, we will use combinations to determine the required probabilities:

X = 1 red marble:

P ( X = 1 ) : Suzan chooses 1 Red marble from the available 3 red marble and 2 green marbles.

P ( X = 1 ) = [ 3C1*2C2 ] / all outcomes = (3*1) / 10 = 0.3

X = 2 red marble:

P ( X = 2 ) : Suzan chooses 2 Red marble from the available 3 red marble and 1 green marbles.

P ( X = 2 ) = [ 3C2*2C1 ] / all outcomes = (3*2) / 10 = 0.6

X = 3 red marble:

P ( X = 3 ) : Suzan chooses 3 Red marble from the available 3 red marble.

P ( X = 3 ) = [ 3C3] / all outcomes = (1) / 10 = 0.1

- The probability distribution is as follows:

X : 1 2 3

P (X): 0.3 0.6 0.1

- The expected value E(X) for the given random variable X is:

E ( X ) = ∑Xi*P(Xi)

= 1*0.3 + 2*0.6 + 3*0.1

=1.8

- The variance Var(X) for the given random variable X is:

Var ( X ) = ∑Xi^2*P(Xi) - [ E(X) ] ^2

= 1^2*0.3 + 2^2*0.6 + 3^2*0.1 - 1.8^2

= 0.36

- The standard deviation for the given random variable X is:

σ = √Var(X)

σ = √0.36

σ = 0.6

5 0

4 years ago

A chameleon is looking for prey. Let positive numbers represent the elevation of prey above the chameleon and negative numbers r

alexira [117]

Answer:

B: The elevation of the chameleon

Step-by-step explanation:

The Fly is above the chameleon, so its elevation should be represented by a "positive number"(Example of positive number: 16)

Also,

The Grasshopper is below the chameleon, so its elevation should be represented by a "negative number"(Example of negative number: -23)

ඞHope this helps u because i got dis question from Khan Academyඞ

4 0

3 years ago

The diameter of a sphere is 4 centimeters.

ELEN [110]

The volume of a sphere refers to the number of cubic units that will exactly fill a sphere. The volume of a sphere can be found or calculate by using the formula V=4/3πr^3, where r represents the radius of the figure.

In this exercise is given that a sphere has a radius of 4 centimeters and it is asked to find its volume and use 3.14 as the value of π or pi. The first step would be substitute the values into the previous mention formula.

V=4/3πr^3
V=4/3(3.14)(4 cm)^3
V=4/3)(3.14)(64 cm^3)
V=267.9 cm^3
The volume of the sphere is 267.9 cubic centimeters.

7 0

3 years ago

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