8. Find x and why please

Suppose that X is a random variable with mean 20 and standard deviation 5. Also

GaryK [48]

Disregard my earlier question.

Recall that the variance of a random variable $X$ , denoted $\mathbb V(X)$ , is given by

$\mathbb E((X-\mu)^2)$

where $\mathbb E(X)$ denotes the expected value/mean of $X$ , and $\mu=\mathbb E(X)$ is the actual mean of $X$ .

Now, recall that

$\mathbb V(X)=\mathbb E((X-\mu)^2)=\mathbb E(X^2-2\mu X+\mu^2)$
$\mathbb V(X)=\mathbb E(X^2)-2\mu^2+\mu^2$
$\mathbb V(X)=\mathbb E(X^2)-\mathbb E(X)^2$

(a) $Z=2+10X$

$\mathbb V(Z)=\mathbb E((2+10X)^2)-\mathbb E(2+10X)^2$
$\mathbb V(Z)=\mathbb E(4+40X+100X^2)-(\mathbb E(2)+\mathbb E(10X))^2$
$\mathbb V(Z)=\mathbb E(4)+40\mathbb E(X)+100\mathbb E(X^2)-(\mathbb E(2)+10\mathbb E(X))^2$
$\mathbb V(Z)=100\mathbb E(X^2)-40000$
$\mathbb V(Z)=100\left(\mathbb E(X^2)-\mathbb E(X)^2+\mathbb E(X)^2\right)-40000$
$\mathbb V(Z)=100\left(\mathbb V(X)+\mathbb E(X)^2\right)-40000$
$\mathbb V(Z)=100\left(5^2+400\right)-40000$
$\mathbb V(Z)=2500$

The standard deviation is the square root of the variance, so for (a) you have

$\sqrt{\mathbb V(Z)}=\sqrt{2500}=50$

That should give you an idea as to how to figure out the rest.

6 0

3 years ago

If there are 24 men and 28 women on an airplane, what is the ratio of women to men in simplest form?

NISA [10]

Answer: c

Step-by-step explanation:

men- 24

women- 28

for every 6 men there are 7 women on the plane bc 28/24= 1.16

1.16 x 6=7 women

7 0

3 years ago

4a² + 2ab+362 -a^2- 3ab +62 Add them

never [62]

Answer:

4a^2+2ab+362 = 2(2a^2+ab+181)

-a^2-3ab+62 = -(3ab+a^2-62)

Step-by-step explanation: For question #1, factor 2 out of 4a^2+2ab+362.

For question #2, factor -1 out of -a^2-3ab+62.

Hope this helps you out.

-Leif Jonsi-

3 0

3 years ago

Anyone knows this?!

Strike441 [17]

Answer:

Option B

Step-by-step explanation:

Step 1: Determine the range and domain

Range is asking for what y values are being used. We can see that the vertex of the parabola is at y = 4 so we know that anything equal or above 4 would be included in the range.

Domain is asking for what x values are being used. We can see that the parabola is pointing in both the negative and positive x direction which means that it will go to infinity on both sides. This gives us the answer that the domain is all real numbers.

Looking at the given options, options C and D are automatically removed because the range is incorrect. Next looking at the domain we see that option A is incorrect which leaves us with option B.

Answer: Option B

5 0

2 years ago

A copy machine can print

Y_Kistochka [10]

Answer:

1200 copies

Step-by-step explanation:

We can use ratios to solve

480 copies x copies

------------------ = -------------

4 minutes 10 minutes

Using cross products

480* 10 = 4x

Divide each side by 4

4800/4 = 4x/4

1200 =x

3 0

4 years ago

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