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3 years ago

PLEASE HELP ME AHHHHHHHHHHHHH

Mathematics

2 answers:

Keith_Richards [23]3 years ago

4 0

Answer:

Step-by378 marbles are blue, and 270 marbles are red

Step-by-step explanation:

The total number of ratio units must be multiplied by 6 to get the total number of marbles. Hence the number of blue marbles is 63×6 = 378, and the number of red marbles is 45×6 = 270.

Read more on Brainly.com - brainly.com/question/11727697#readmore-step explanation:

serg [7]3 years ago

3 0

Answer:

378 marbles are blue, and 270 marbles are red

Step-by-step explanation:

The total number of ratio units must be multiplied by 6 to get the total number of marbles. Hence the number of blue marbles is 63×6 = 378, and the number of red marbles is 45×6 = 270.

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Assume that the helium porosity (in percentage) of coal samples taken from any particular seam is normally distributed with true

Feliz [49]

Answer:

a) The 95% CI for the true average porosity is (4.51, 5.19).

b) The 98% CI for true average porosity is (4.11, 5.01)

c) A sample size of 15 is needed.

d) A sample size of 101 is needed.

Step-by-step explanation:

a. Compute a 95% CI for the true average porosity of a certain seam if the average porosity for 20 specimens from the seam was 4.85.

We have that to find our $\alpha$ level, that is the subtraction of 1 by the confidence interval divided by 2. So:

$\alpha = \frac{1-0.95}{2} = 0.025$

Now, we have to find z in the Ztable as such z has a pvalue of $1-\alpha$ .

So it is z with a pvalue of $1-0.025 = 0.975$ , so $z = 1.96$

Now, find the margin of error M as such

$M = z*\frac{\sigma}{\sqrt{n}}$

In which $\sigma$ is the standard deviation of the population and n is the size of the sample.

$M = 1.96*\frac{0.78}{\sqrt{20}} = 0.34$

The lower end of the interval is the sample mean subtracted by M. So it is 4.85 - 0.34 = 4.51

The upper end of the interval is the sample mean added to M. So it is 4.35 + 0.34 = 5.19

The 95% CI for the true average porosity is (4.51, 5.19).

b. Compute a 98% CI for true average porosity of another seam based on 16 specimens with a sample average of 4.56.

Following the same logic as a.

98% C.I., so $z = 2.327$

$M = 2.327*\frac{0.78}{\sqrt{16}} = 0.45$

4.56 - 0.45 = 4.11

4.56 + 0.45 = 5.01

The 98% CI for true average porosity is (4.11, 5.01)

c. How large a sample size is necessary if the width of the 95% interval is to be 0.40?

A sample size of n is needed.

n is found when M = 0.4.

95% C.I., so Z = 1.96.

$M = z*\frac{\sigma}{\sqrt{n}}$

$0.4 = 1.96*\frac{0.78}{\sqrt{n}}$

$0.4\sqrt{n} = 1.96*0.78$

$\sqrt{n} = \frac{1.96*0.78}{0.4}$

$(\sqrt{n})^{2} = (\frac{1.96*0.78}{0.4})^{2}$

$n = 14.6$

Rounding up

A sample size of 15 is needed.

d. What sample size is necessary to estimate the true average porosity to within 0.2 with 99% confidence?

99% C.I., so z = 2.575

n when M = 0.2.

$M = z*\frac{\sigma}{\sqrt{n}}$

$0.2 = 2.575*\frac{0.78}{\sqrt{n}}$

$0.2\sqrt{n} = 2.575*0.78$

$\sqrt{n} = \frac{2.575*0.78}{0.2}$

$(\sqrt{n})^{2} = (\frac{2.575*0.78}{0.2})^{2}$

$n = 100.85$

Rounding up

A sample size of 101 is needed.

8 0

4 years ago

3x+1/10=x-1/7 what is x explain how you got the answer please do a step by step solution

polet [3.4K]

Ok, to solve an algebraic equation we need to get the unknown by itself on one side of the equals sign. To do that, basically we just have to cancel everything else out... but whatever we do to cancel out what we don't want, we also have to do on the other side of the equals sign...

3x + 1/10 = x - 1/7

Let's start by getting the x on the right over to the left side. To cancel it from the right side we have to subtract it (x-x = 0). Don't forget to subtract it on the left also.

3x -x + 1/10 = x - x - 1/7

Now combine like terms

2x + 1/10 = -1/7

Now let's bring the 1/10 over to the right of the equals sign to get x by itself by subtracting it.

2x + 1/10 - 1/10 = -1/7 - 1/10

Combine like terms

2x = -1/7 - 1/10

Let's get a common denominator so we can combine the fractions

2x = -10/70 - 7/70
2x = -17/70

Now divide both sides by 2 to finish getting x by itself. To divide fractions, multiply the reciprocal.

x = -17/70 x 1/2
x = -17/140

6 0

4 years ago

775 tickets were sold for a game for a total of 1,187.50. If adults tickets sold for 2.50 and children's tickets sold for 1.00 h

Ivanshal [37]

Answer: 275 adult tickets and 500 children's tickets were sold.

Step-by-step explanation:

Let x represent the number of adult tickets that were sold.

Let y represent the number of children's tickets that were sold.

775 tickets were sold for the game. It means that

x + y = 775

If adults tickets sold for 2.50 and children's tickets sold for 1.00 and all the tickets were sold for a total of 1,187.50, it means that

2.5x + y = 1187.5

Substituting x = 775 - y into equation 1, it becomes

2.5(775 - y) + y = 1187.5

1937.5 - 2.5y + y = 1187.5

- 2.5y + y = 1187.5 - 1937.5

- 1.5y = - 750

y = - 750/ - 1.5

y = 500

x = 775 - y = 775 - 500

x = 275

6 0

3 years ago

One railroad track was laid out on the line y = 8x - 2 by the engineers in charge. Which of the following lines could have been

kvv77 [185]

Y = 8x - 2.....slope here is 8. A parallel line will have the same slope.

The other line would be : y = 4 + 8x (or y = 8x + 4).....because they both have the same slope, which makes the lines parallel to each other

7 0

4 years ago

Read 2 more answers

A rectangle has a width of 9 units and a length of 40 units. What is the length of a diagonal?

aliina [53]

Answer:

41 units

Step-by-step explanation:

Rectangles have right angles, so we can use Pythagorean theorem to find the diagonal.

c² = a² + b²

c² = 9² + 40²

c² = 81 + 1600

c² = 1681

c = 41

4 0

4 years ago