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3 years ago

How many hours is 8 to 3 o'clock

Mathematics

2 answers:

julsineya [31]3 years ago

6 0

There will be 7 hours

sammy [17]3 years ago

4 0

8 to 12 is 4 hours and 12 to 3 is 3 hours. So the total hours is 7 hours

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What is the square root of 81

Talja [164]

The square root of 81 is 9

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3 years ago

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If b < 0 and a/b > c/b, then what is the relationship between a and c?

serg [7]

Answer:

a < c

Step-by-step explanation:

<u>Given inequality:</u>

a/b > c/b

<u>Since b is negative, when multiplied by b, the inequality changes to opposite direction:</u>

b(a/b) < b(c/b)
a < c

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2 years ago

Match the equivalent expressions

kakasveta [241]

The picture is very blurry I can’t see

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3 years ago

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Please answer correctly !!!!!! Will mark brainliest answer !!!!!!!!!!

Rasek [7]

Answer:

see below

Step-by-step explanation:

1. 0 = (r + 1)(r + 8)

Using Zero Product Property, r = -1, r = -8

2. h(r) = (r + 1)(r + 8)

= r² + 9r + 8

= (r + 9/2)² - 81/4 + 8

= (r + 4.5)² - 12.25 (Complete the square)

Vertex: (-4.5, -12.25)

5 0

3 years ago

GRE Test: The Graduate Record Examination (GRE) is a test required for admission to many US graduate schools. Student’s scores o

Zepler [3.9K]

Answer:

a) $\bar X=144.3$

b) The 95% confidence interval would be given by (138.846;149.754)

c) n=34

d) n=298

e) n=1190

Step-by-step explanation:

Previous concepts

A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".

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".

We can calculate the sample mean with this formula:

$\bar X = \frac{\sum_{i=1}^n x_i}{n}$

$\bar X=144.3$ represent the sample mean

$\mu$ population mean (variable of interest)

$\sigma=8.8$ represent the population standard deviation

n=10 represent the sample size

a) Find a point estimate of the population mean

We can calculate the sample mean with this formula:

$\bar X = \frac{\sum_{i=1}^n x_i}{n}$

$\bar X=144.3$

b) Construct a 95% confidence interval for the true mean score for this population.

The confidence interval for the mean is given by the following formula:

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

Since the Confidence is 0.95 or 95%, the value of $\alpha=0.05$ and $\alpha/2 =0.025$ , and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-NORM.INV(0.025,0,1)".And we see that $t_{\alpha/2}=1.96$

Now we have everything in order to replace into formula (1):

$144.3-1.96\frac{8.8}{\sqrt{10}}=138.846$

$144.3+1.96\frac{8.8}{\sqrt{10}}=149.754$

So on this case the 95% confidence interval would be given by (138.846;149.754)

Part c

The margin of error is given by this formula:

$ME=z_{\alpha/2}\frac{\sigma}{\sqrt{n}}$ (a)

And on this case we have that ME =+20 and we are interested in order to find the value of n, if we solve n from equation (a) we got:

$n=(\frac{z_{\alpha/2} \sigma}{ME})^2$ (b)

The critical value for 95% of confidence interval now can be founded using the normal distribution. And in excel we can use this formla to find it:"=-NORM.INV(0.025;0;1)", and we got $z_{\alpha/2}=1.960$ , replacing into formula (5) we got:

$n=(\frac{1.960(8.8)}{3})^2 =33.05 \approx 34$

So the answer for this case would be n=34 rounded up to the nearest integer

Part d

$n=(\frac{1.960(8.8)}{1})^2 =297.493 \approx 298$

So the answer for this case would be n=298 rounded up to the nearest integer

Part e

$n=(\frac{1.960(8.8)}{0.5})^2 =1189.97 \approx 1190$

So the answer for this case would be n=1190 rounded up to the nearest integer

7 0

3 years ago