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3 years ago

I need help with question 3 part B please !

Mathematics

1 answer:

Alona [7]3 years ago

6 0

Answer:

Yes, one inch is a twlefth of a ft which is a porportion of a feet

Step-by-step explanation:

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Jason’s gas tank can hold 12 gallons of gas. His gas tank was empty and he filled it up 2/3 full. He spent $20.16. How much did

natita [175]

Answer:

$2.52 per gallon.

Explanation:

$\frac{2}{3} \times 12 = 8$

$8c = 20.16$

$c = 2.52$

7 0

2 years ago

Write 3 numbers that make this inequality true: x>4

Trava [24]

Answer:

8, 10, 24

(Basically every number above 4)

5 0

3 years ago

Read 2 more answers

The lifetime X (in hundreds of hours) of a certain type of vacuum tube has a Weibull distribution with parameters α = 2 and β =

stich3 [128]

I'm assuming $\alpha$ is the shape parameter and $\beta$ is the scale parameter. Then the PDF is

$f_X(x)=\begin{cases}\dfrac29xe^{-x^2/9}&\text{for }x\ge0\\\\0&\text{otherwise}\end{cases}$

a. The expectation is

$E[X]=\displaystyle\int_{-\infty}^\infty xf_X(x)\,\mathrm dx=\frac29\int_0^\infty x^2e^{-x^2/9}\,\mathrm dx$

To compute this integral, recall the definition of the Gamma function,

$\Gamma(x)=\displaystyle\int_0^\infty t^{x-1}e^{-t}\,\mathrm dt$

For this particular integral, first integrate by parts, taking

$u=x\implies\mathrm du=\mathrm dx$

$\mathrm dv=xe^{-x^2/9}\,\mathrm dx\implies v=-\dfrac92e^{-x^2/9}$

$E[X]=\displaystyle-xe^{-x^2/9}\bigg|_0^\infty+\int_0^\infty e^{-x^2/9}\,\mathrm x$

$E[X]=\displaystyle\int_0^\infty e^{-x^2/9}\,\mathrm dx$

Substitute $x=3y^{1/2}$ , so that $\mathrm dx=\dfrac32y^{-1/2}\,\mathrm dy$ :

$E[X]=\displaystyle\frac32\int_0^\infty y^{-1/2}e^{-y}\,\mathrm dy$

$\boxed{E[X]=\dfrac32\Gamma\left(\dfrac12\right)=\dfrac{3\sqrt\pi}2\approx2.659}$

The variance is

$\mathrm{Var}[X]=E[(X-E[X])^2]=E[X^2-2XE[X]+E[X]^2]=E[X^2]-E[X]^2$

The second moment is

$E[X^2]=\displaystyle\int_{-\infty}^\infty x^2f_X(x)\,\mathrm dx=\frac29\int_0^\infty x^3e^{-x^2/9}\,\mathrm dx$

Integrate by parts, taking

$u=x^2\implies\mathrm du=2x\,\mathrm dx$

$\mathrm dv=xe^{-x^2/9}\,\mathrm dx\implies v=-\dfrac92e^{-x^2/9}$

$E[X^2]=\displaystyle-x^2e^{-x^2/9}\bigg|_0^\infty+2\int_0^\infty xe^{-x^2/9}\,\mathrm dx$

$E[X^2]=\displaystyle2\int_0^\infty xe^{-x^2/9}\,\mathrm dx$

Substitute $x=3y^{1/2}$ again to get

$E[X^2]=\displaystyle9\int_0^\infty e^{-y}\,\mathrm dy=9$

Then the variance is

$\mathrm{Var}[X]=9-E[X]^2$

$\boxed{\mathrm{Var}[X]=9-\dfrac94\pi\approx1.931}$

b. The probability that $X\le3$ is

$P(X\le 3)=\displaystyle\int_{-\infty}^3f_X(x)\,\mathrm dx=\frac29\int_0^3xe^{-x^2/9}\,\mathrm dx$

which can be handled with the same substitution used in part (a). We get

$\boxed{P(X\le 3)=\dfrac{e-1}e\approx0.632}$

c. Same procedure as in (b). We have

$P(1\le X\le3)=P(X\le3)-P(X\le1)$

and

$P(X\le1)=\displaystyle\int_{-\infty}^1f_X(x)\,\mathrm dx=\frac29\int_0^1xe^{-x^2/9}\,\mathrm dx=\frac{e^{1/9}-1}{e^{1/9}}$

Then

$\boxed{P(1\le X\le3)=\dfrac{e^{8/9}-1}e\approx0.527}$

7 0

3 years ago

Answer all for Brainliest (easy math) 5 questions for 30 points

sweet-ann [11.9K]

1) The caterpillar was already at 4.5 feet so 4.5 will be added. If it crawls upwards 38 of an inch every minute and the amount of minutes is not specified, this will be represented as 38x. That means the answer is C. f(x) = 38x + 4.5

2) Substitute the known values into the equation. There are 7 people at $8.25 a person, which is a total of $57.75 <u>I used 7 because he invites 6 friends, plus himself. </u>He only has $50 on his gift card, so he won't have enough to cover the cost. The answer is A.

3) They start out with 40lbs and recieve 120 more. They have 160lbs in total. If they sell 8lbs a day for 5 days, thats 8*5 or 40lbs total. 160 - 40 = 120lbs left after 5 days. I'd say the answers are A, B, and D.

4) I think the answer would be C because 1,500 is used to find the number of grams of isotope present after t years. The number of grams can't be 1,500. I hope that makes sense because I'm not sure how to explain it.

5) The growth factor is 2 (2x, x being the number of hours). Multiply by 15 because the lab has 15 of them. The answer is B. f(x) = 15 * 2x

I hope this helps you! I'm sorry if I got any of them wrong!

7 0

3 years ago

What is y over 3 (y/3) = 12

PSYCHO15rus [73]

Answer:

so what i would like to do is what is 12 divid by 3 and when u get ur answer that it what the y is

7 0

3 years ago

Read 2 more answers