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3 years ago

Please Help I’ve been stuck on these questions for a while now!

Mathematics

1 answer:

atroni [7]3 years ago

8 0

Answer:

written below for problem #2

Step-by-step explanation:

a. ratio is 12:40 since they're are 12 non fiction and 40 graphic novels

b. 40:12 (same reasoning as part a)

c. 6:40 for the ratio of science fiction to graphic novel, 12:6 for the ration of non fiction to science fiction, x:6 for the ratio of the unknown amount of fiction books to the science fiction books. (x is just there as a variable so it just represents fiction books)

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Read 2 more answers

3x - 5y = 14 and – 2x + 2y = 0

zubka84 [21]

Answer:

x=5.6

y=-5.6

Step-by-step explanation:

3x - 5y = 14 Equation 1

– 2x + 2y = 0 Equation 2

Simultaneous equation can be solved either through elimination method or substitution method. But we use elimination method for this question

Multiply equation 1 by -2 (the coefficient of x in equation 2) and multiply equation 2 with 3 (the coefficient of x in equation 1), so that x will have the same coefficient in the new equations, and easy to eliminate

-2(3x - 5y = 14)

-6x+10y=-28 Equation 3

3(– 2x + 2y = 0)

-6x+6y=0 Equation 4

Subtract equation 4 from 3 to eliminate x

-6x+10y=-28

-6x+6y=0

-6x-(-6x)=-6x+6x=0

10y-6y=5y

-28-0=-28

5y=-28

y=-28/5

y=-5.6

Substitute for y in equation 2

– 2x + 2y = 0

– 2x + 2(-5.6) = 0

-2x-11.2=0

-2x=11.2

x=-11.2/2

x=5.6

7 0

3 years ago

Suppose that the population of the scores of all high school seniors who took the SAT Math (SAT-M) test this year follows a Norm

Vlad1618 [11]

Answer:

Confidence = $1-\alpha=1-0.01=0.99$

And then the confidence level would be given by 99%

Step-by-step explanation:

The margin of error is the range of values below and above the sample statistic in a confidence interval.

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".

Assuming the X follows a normal distribution

$X \sim N(\mu, \sigma)$

The distribution for the sample mean is given by:

$\bar X \sim N(\mu, \frac{\sigma}{\sqrt{n}})$

$\bar x =512$ represent the sample mean

$\sigma=100$ represent the population standard deviation

n= 100 sample size selected.

The confidence interval is given by this formula:

$\bar X \pm z_{\alpha/2} \frac{\sigma}{\sqrt{n}}$ (1)

The marginof error for this case is given by Me=25.76. And we know that the formula for the margin of error is given by:

$Me=z_{\alpha/2} \frac{\sigma}{\sqrt{n}}$

$25.76=z_{\alpha/2} \frac{100}{\sqrt{100}}$

And we can find the critical value $z_{\alpha/2}$ like this:

$z_{\alpha/2}=\frac{25.76(\sqrt{100})}{100}=2.576$

And we know that on the right tail of the z score =2.576 we have $\alpha/2$ of the total area. We can find the area on the right of the z score using this excel code:

"=1-NORM.DIST(2.576,0,1,TRUE)" or using a table of the normal standard distribution, and we got 0.004998= $\alpha/2$ , so then $\alpha=0.00498*2=0.009995 \approx 0.01$ , and then we can find the confidence like this:

Confidence = $1-\alpha=1-0.01=0.99$

And then the confidence level would be given by 99%

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3 years ago