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3 years ago

Please help I don't understand

Mathematics

1 answer:

Papessa [141]3 years ago

7 0

Answer:

A 200

Step-by-step explanation:

The total price of the items solve was 1185

Take the low end of the price range or 4

Divide 1185 by 4

1185/4 =296.25 items could be sold for 4 dollars

Take the high end of the price range or 8

Divide 1185 by 8

1185/8 =148.125 items could be sold for 8 dollars

The number of items sold must be somewhere in between these two numbers.

148< number of items sold < 296

The only item on the list is 200

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23. A certain type of gasoline is supposed to have a mean octane rating of at least 90. Suppose measurements are taken on of 5 r

Nostrana [21]

Answer:

a) $p_v =P(Z$

b) Since $p_v$ we can reject the null hypothesis at the significance level given. So based on this we can commit type of Error I.

Because Type I error " is the rejection of a true null hypothesis".

c) $P(\bar X >90)=1-P(Z$

$1-P(Z$

d) For this case we need a z score that accumulates 0.02 of the area on the right tail and 0.98 on the left tail and this value is z=2.054

And we can use this formula:

$2.054=\frac{90-89}{\frac{0.8}{\sqrt{n}}}$

And if we solve for n we got:

$n = (\frac{2.054 *0.8}{1})^2=2.7 \approx 3$

Step-by-step explanation:

Previous concepts and data given

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 and deviation with the following formulas:

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

$s=\sqrt{\sum_{i=1}^n (X_i -\bar X)^2}{n-1}$

$\bar X=88.96$ represent the sample mean

$s=1.011$ represent the sample standard deviation

n=5 represent the sample selected

$\alpha$ significance level

State the null and alternative hypotheses.

We need to conduct a hypothesis in order to check if the mean is less than 90, the system of hypothesis would be:

Null hypothesis: $\mu \geq 90$

Alternative hypothesis: $\mu < 90$

If we analyze the size for the sample is < 30 and we don't know the population deviation so is better apply a t test to compare the actual mean to the reference value, and the statistic is given by:

$z=\frac{\bar X-\mu_o}{\frac{\sigma}{\sqrt{n}}}$ (1)

z-test: "Is used to compare group means. Is one of the most common tests and is used to determine if the mean is (higher, less or not equal) to an specified value".

Calculate the statistic

We can replace in formula (1) the info given like this:

$z=\frac{88.96-90}{\frac{0.8}{\sqrt{5}}}=-2.907$

Part a

P-value

First we need to calculate the degrees of freedom given by:

$df=n-1=5-1 = 4$

Then since is a left tailed test the p value would be:

$p_v =P(Z$

Part b

Since $p_v$ we can reject the null hypothesis at the significance level given. So based on this we can commit type of Error I.

Because Type I error " is the rejection of a true null hypothesis".

Part c

We want this probability:

$P(\bar X$

The best way to solve this problem is using the normal standard distribution and the z score given by:

$z=\frac{x-\mu}{\frac{\sigma}{\sqrt{n}}}$

If we apply this formula to our probability we got this:

$P(\bar X >90)=1-P(Z$

$1-P(Z$

Part d

For this case we need a z score that accumulates 0.02 of the area on the right tail and 0.98 on the left tail and this value is z=2.054

And we can use this formula:

$2.054=\frac{90-89}{\frac{0.8}{\sqrt{n}}}$

And if we solve for n we got:

$n = (\frac{2.054 *0.8}{1})^2=2.7 \approx 3$

7 0

3 years ago

PLZ HELP ASAP ANGLE BISECTOR THEOREM

ycow [4]

Angle bisector theorem:
CD/DB=AC/AB
REeplacing the known values:
CD/4=5.6/5.1
Solving for CD. Multiplying both sides of the equation by 4:
4(CD/4)=4(5.6/5.1)
CD=22.4/5.1
CD=4.392156863
Rounded to one decimal place:
CD=4.4

Answer: The length of CD is 4.4

7 0

3 years ago

The radioactive substance polonium-210, with a half-life of 138.39 days, is present in tobacco. Suppose that the soot in an ex-s

Ksju [112]

Answer:

16.07 milligrams

Step-by-step explanation:

From the question,

Using the formula of radioactive decay,

R/R' = 2ᵃ/ᵇ..................... Equation 1

Where R = Original mass of the polonium-210, R' = Final mass of polonium-210 after decaying, a = Total disintegration time, b = half life of polonium-210.

Make R' the subject of the equation

R' = R/(2ᵃ/ᵇ)................ Equation 2

Given: R = 100 milligrams, a = 1 years = 365 days, b = 138.39 days

Substitute these values into equation 2

R' = 100/(2³⁶⁵⁰⁰/¹³⁸³⁹)

R' = 100/(6.222)

R' = 16.07 milligrams of plonium-210

3 0

2 years ago

The sum of a number and its square is 2. Find the number(s).

Yuliya22 [10]

Let x represent the number.
.. x^2 +x = 2
.. x^2 +x +1/4 = 9/4 . . . . add 1/4 to complete the square
.. x +1/2 = ±3/2 . . . . . . . .square root
.. x = -2, 1

Numbers meeting that requirement are -2 and 1.

6 0

3 years ago

Match the key aspect of a function's graph with its meaning.

Margarita [4]

Answer:

Part 1) Intervals of the domain where the graph is above the x-axis (f(x) > 0)

Part 2) location on graph where input is zero (y-intercept)

Part 3) location on graph where output is zero (x-intercept)

Part 4) Intervals of the domain where the graph is below the x-axis (f(x) < 0)

Step-by-step explanation:

<u><em>Verify each case</em></u>

Part 1) we have

Intervals of the domain where the graph is above the x-axis

we know that

If the graph is above the x-axis, then the value of f(x) is positive

therefore

f(x) > 0

Part 2) we have

location on graph where input is zero

Let

x ---> the independent variable or input value

f(x) ---> the dependent variable or output value

we know that

The y-intercept is the value of f(x) (output value) when the value of x (input value) is zero

therefore

y-intercept

Part 3) we have

location on graph where output is zero

Let

x ---> the independent variable or input value

f(x) ---> the dependent variable or output value

we know that

The x-intercept is the value of x (input value) when the value of the function f(x) (output value) is zero

therefore

x-intercept

Part 4) we have

Intervals of the domain where the graph is below the x-axis

we know that

If the graph is below the x-axis, then the value of f(x) is negative

therefore

f(x) < 0

5 0

3 years ago

Please help I don't understand ​

Please help I don't understand