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3 years ago

8

On a city map, Dan lives at D(-6,5) and Bill lives at B(0,2). How far apart do they live? Remember to reduce the radical, if the

re is a square root in the answer type sqrt with no spaces, example 5sqrt3.

1 answer:

Alinara [238K]3 years ago

6 0

√ [(0-(-6)) ² +(5-2) ²]

=√ [(6) ²+(3) ²]

=√ [36+9]

=√ 45

=3 √ 5

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Point Coordinate

telo118 [61]

Step 1:

First, let's order the number from least to greatest.

A. -0.31

B. -0.33

C. -0.38

D. -0.29

We could see that A, B, and C's numbers are already from least to greatest, so all we have to do is to move -0.29 (D) up to the top, since -0.29 is the number with the lowest value.

C. -0.38

B. -0.33

A. -0.31

D. -0.29

Step 2:

Let's look at the four number lines. Remember that we already organized the numbers from least to greatest, so the order they go in on the number line is: C, B, A, and D. Since Line C and D Don't follow that rule, we know those are not our answers. Also on line B, C is on the left of -0.4, but C's value is less than -0.4, so B is wrong. We are left with line A.

Line A: C. -0.38, B. -0.33, A. -0.31, D. -0.29

Our answer: Line A

5 0

3 years ago

I need help with this, it’s counting principles but I don’t know how to do it! Help

aliina [53]

The answer is 2^12 = 4096.

Look at a tree diagram. With one spin there are two possible outcomes (branches). Every time you spin, each of the branches split into two more branches.
With 12 spins, first there are 2 branches, then 2*2, then 2*2*2, ... In the end it's 2^12

7 0

3 years ago

Suppose that W1, W2, and W3 are independent uniform random variables with the following distributions: Wi ~ Uni(0,10*i). What is

nadya68 [22]

I'll leave the computation via R to you. The $W_i$ are distributed uniformly on the intervals $[0,10i]$ , so that

$f_{W_i}(w)=\begin{cases}\dfrac1{10i}&\text{for }0\le w\le10i\\\\0&\text{otherwise}\end{cases}$

each with mean/expectation

$E[W_i]=\displaystyle\int_{-\infty}^\infty wf_{W_i}(w)\,\mathrm dw=\int_0^{10i}\frac w{10i}\,\mathrm dw=5i$

and variance

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

We have

$E[{W_i}^2]=\displaystyle\int_{-\infty}^\infty w^2f_{W_i}(w)\,\mathrm dw=\int_0^{10i}\frac{w^2}{10i}\,\mathrm dw=\frac{100i^2}3$

so that

$\mathrm{Var}[W_i]=\dfrac{25i^2}3$

Now,

$E[W_1+W_2+W_3]=E[W_1]+E[W_2]+E[W_3]=5+10+15=30$

and

$\mathrm{Var}[W_1+W_2+W_3]=E\left[\big((W_1+W_2+W_3)-E[W_1+W_2+W_3]\big)^2\right]$

$\mathrm{Var}[W_1+W_2+W_3]=E[(W_1+W_2+W_3)^2]-E[W_1+W_2+W_3]^2$

We have

$(W_1+W_2+W_3)^2={W_1}^2+{W_2}^2+{W_3}^2+2(W_1W_2+W_1W_3+W_2W_3)$

$E[(W_1+W_2+W_3)^2]$

$=E[{W_1}^2]+E[{W_2}^2]+E[{W_3}^2]+2(E[W_1]E[W_2]+E[W_1]E[W_3]+E[W_2]E[W_3])$

because $W_i$ and $W_j$ are independent when $i\neq j$ , and so

$E[(W_1+W_2+W_3)^2]=\dfrac{100}3+\dfrac{400}3+300+2(50+75+150)=\dfrac{3050}3$

giving a variance of

$\mathrm{Var}[W_1+W_2+W_3]=\dfrac{3050}3-30^2=\dfrac{350}3$

and so the standard deviation is $\sqrt{\dfrac{350}3}\approx\boxed{116.67}$

# # #

A faster way, assuming you know the variance of a linear combination of independent random variables, is to compute

$\mathrm{Var}[W_1+W_2+W_3]$

$=\mathrm{Var}[W_1]+\mathrm{Var}[W_2]+\mathrm{Var}[W_3]+2(\mathrm{Cov}[W_1,W_2]+\mathrm{Cov}[W_1,W_3]+\mathrm{Cov}[W_2,W_3])$

and since the $W_i$ are independent, each covariance is 0. Then

$\mathrm{Var}[W_1+W_2+W_3]=\mathrm{Var}[W_1]+\mathrm{Var}[W_2]+\mathrm{Var}[W_3]$

$\mathrm{Var}[W_1+W_2+W_3]=\dfrac{25}3+\dfrac{100}3+75=\dfrac{350}3$

and take the square root to get the standard deviation.

8 0

3 years ago

Eric's apartment is 1350 s1quare feet, how many square meters of carpet will he need to order?

ArbitrLikvidat [17]

Answer:

He needs to order $125.42\ m^{2}$ of carpet

Step-by-step explanation:

we know that

$1\ ft=0.3048\ m$

we have

$1,350\ ft^{2}$

Convert to $m^{2}$

$1,350\ ft^{2}=1,350(0.3048)^{2}=125.42\ m^{2}$

6 0

3 years ago

Read 2 more answers

Rectangle has sides that are 25 m, 25m, 9m, and 9 m. What is the rectangle’s width?

Dmitrij [34]

9m
It said the sides are 25m (x2) and 9m(x2). The width of a rectangle are shorter than the length so 9m.

7 0

2 years ago