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3 years ago

PLEASE HELP ASAP....i’ll mark brainlest

Mathematics

1 answer:

Sidana [21]3 years ago

8 0

Answer:

True

Step-by-step explanation:

Kilo means 1,000 so kilometers means 1,000 meters. If you don't know prefixes it might be kind of confusing because centimeters doesn't mean 100 meters so I'll leave something here.

Kilometers = 1000 meters

1 meter = 10 decimeters

1 decimeter = 10 centimeters

1 centimeter = 10 millimeters

If I have time later I'll attach a visual that could help.

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Help is greatly appreciated:)

Murrr4er [49]

Well there are 6 units down and 11 units across so 6•11=66. there are 14 red units. 66-14=52. the area of yellow is 52.

4 0

3 years ago

A building has n floors numbered 1,2,...,n, plus a ground floor g. at the ground floor, m people get on the elevator together, a

fomenos

Let $X_i$ be the random variable indicating whether the elevator does not stop at floor $i$ , with

$X_i=\begin{cases}1&\text{if the elevator does not stop at floor }i\\0&\text{otherwise}\end{cases}$

Let $Y$ be the random variable representing the number of floors at which the elevator does not stop. Then

$Y=X_1+X_2+\cdots+X_{n-1}+X_n$

We want to find $\mathrm{Var}(Y)$ . By definition,

$\mathrm{Var}(Y)=\mathbb E[(Y-\mathbb E[Y])^2]=\mathbb E[Y^2]-\mathbb E[Y]^2$

As stated in the question, there is a $\dfrac1n$ probability that any one person will get off at floor $n$ (here, $n$ refers to any of the $n$ total floors, not just the top floor). Then the probability that a person will not get off at floor $n$ is $1-\dfrac1n$ . There are $m$ people in the elevator, so the probability that not a single one gets off at floor $n$ is $\left(1-\dfrac1n\right)^m$ .

So,

$\mathbb P(X_i=x)\begin{cases}\left(1-\dfrac1n\right)^m&\text{for }x=1\\\\1-\left(1-\dfrac1n\right)^m&\text{for }x=0\end{cases}$

which means

$\mathbb E[Y]=\mathbb E\left[\displaystyle\sum_{i=1}^nX_i\right]=\displaystyle\sum_{i=1}^n\mathbb E[X_i]=\sum_{i=1}^n\left(1\cdot\left(1-\dfrac1n\right)^m+0\cdot\left(1-\left(1-\dfrac1n\right)^m\right)$
$\implies\mathbb E[Y]=n\left(1-\dfrac1n\right)^m$

and

$\mathbb E[Y^2]=\mathbb E\left[\left(\displaystyle\sum_{i=1}^n{X_i}\right)^2\right]=\mathbb E\left[\displaystyle\sum_{i=1}^n{X_i}^2+2\sum_{1\le i$

Computing $\mathbb E[{X_i}^2]$ is trivial since it's the same as $\mathbb E[X_i]$ . (Do you see why?)

Next, we want to find the expected value of the following random variable, when $i\neq j$ :

$X_iX_j=\begin{cases}1&\text{if }X_i=1\text{ and }X_j=1\\0&\text{otherwise}\end{cases}$

If $X_iX_j=0$ , we don't care; when we compute $\mathbb E[X_iX_j]$ , the contributing terms will vanish. We only want to see what happens when both floors are not visited.

$\mathbb P(X_iX_j=1)=\left(1-\dfrac2n\right)^m$
$\implies\mathbb E[X_iX_j]=\left(1-\dfrac2n\right)^m$
$\implies2\displaystyle\sum_{1\le i$

where we multiply by $n(n-1)$ because that's how many ways there are of choosing indices $i,j$ for $X_iX_j$ such that $1\le i$ .

So,

$\mathrm{Var}[Y]=n\left(1-\dfrac1n\right)^m+2n(n-1)\left(1-\dfrac2n\right)^m-n^2\left(1-\dfrac1n\right)^{2m}$

4 0

3 years ago

Answer fast please .

MArishka [77]

I think it's D. The area of A is k2 times the area of rectangle B

8 0

3 years ago

The measure of ∠BCD is 120°. The measure of ∠ABC is 85°.<br><br><br><br> What is measure of ∠BAC?

Ivanshal [37]

First of all, triangles angles add up to 180 degrees.

BCD=120. To find BCA subtract 180-120 to get 60 degrees.

We know what ABC is, it equals 85, so far we have 2 angles.

Lets add them up, 85+60=145

Since the angles must add up to equal 180 we're going to subtract 180-145

Which equals 35, BAC=35 degrees.

-Seth

6 0

3 years ago

Read 2 more answers

Math please help give u brainlist

RoseWind [281]

Answer:

Step-by-step explanation:

(0,-4) (-4, -3)

-3- -4 / -4 -0 = 1/-4 is the slope

so is C

7 0

3 years ago

Read 2 more answers