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coldgirl [10]
2 years ago
12

A thumbtack that is tossed can land point up or point down. The probability of a tack landing point up is 0.2. A simulation was

conducted in which a trial consisted of tossing 5 thumbtacks and recording the number of thumbtacks that land point up. Many trials of the simulation were conducted and the results are shown in the histogram.
Based on the results of the simulation, which of the following is closest to the probability that at least 2 thumbtacks land pointing up when 5 thumbtacks are tossed?

A 0.09

B 0.19

C 0.28

D 0.72

E 0.91

Mathematics
2 answers:
sweet-ann [11.9K]2 years ago
8 0

Answer:

Option C: 0.28

Step-by-step explanation:

This is a binomial probability distribution problem.

Now, we want to find the probability that at least 2 thumbtacks land pointing up when 5 thumbtacks are tossed. This is written as;

P(X ≥ 2) = P(2) + P(3) + P(4) + P(5)

From the histogram;

P(5) = 0.02

P(4) = 0.02

P(3) = 0.05

P(2) = 0.19

Thus;

P(X ≥ 2) = 0.19 + 0.05 + 0.02 + 0.02

P(X ≥ 2) = 0.28

Delvig [45]2 years ago
7 0

Answer:

0.28

Step-by-step explanation:

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A marketing firm wants to estimate how much root beer the average teenager drinks per year. A previous study found a standard de
Verdich [7]

Answer:

At least 832 teenargers must be interviewed.

Step-by-step explanation:

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

\alpha = \frac{1-0.99}{2} = 0.005

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 1-0.005 = 0.995, so z = 2.575

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.

How many teenagers must the firm interview in order to have a margin of error of at most 0.1 liter when constructing a 99% confidence interval

At least n teenargers must be interviewed.

n is found when M = 0.1.

We have that \sigma = 1.12

So

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

0.1 = 2.575*\frac{1.12}{\sqrt{n}}

0.1\sqrt{n} = 2.575*1.12

\sqrt{n} = \frac{2.575*1.12}{0.1}

(\sqrt{n})^{2} = (\frac{2.575*1.12}{0.1})^{2}

n = 831.7

Rounding up

At least 832 teenargers must be interviewed.

4 0
2 years ago
It takes 5 carpenters 5 hours to make 5 chairs. How long would it take 100 carpenters to make 100 chairs?
Elza [17]
I hour because, one of the 5 carpenters built one chair in one hour, so one of the 100 carpenters would build one chair in one hour, there are only 95 more carpenters, nothing else different.
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2 years ago
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A circular platform is to be built in a playground. The center of the structure is required to be equidistant from three support
castortr0y [4]

Answer:

The coordinates for the location of the center of the platform are (0, 1)

Step-by-step explanation:

The equation of the circle of center (h , k) and radius r is:

(x - h)² + (y - k)² = r²

Now,

- The center is equidistant from any point lies on the circumference of the circle

- There are three points equidistant from the center of the circle

- We have three unknowns in the equation of the circle h , k , r

Thus, let's substitute the coordinates of these point in the equation of the circle to find h , k , r.

The equation of the circle is (x - h)² + (y - k)² = r²

∵ Points A(2,−3), B(4,3), and C(−2,5)

- Substitute the values of x and y the coordinates of these points

Point A (2 , -3)

(2 - h)² + (-3 - k)² = r² - - - (1)

Point B (4 , 3)

(4 - h)² + (3 - k)² = r² - - - - (2)

Point C (-2 , 5)

(-2 - h)² + (5 - k)² = r² - - - - (3)

- To find h , k equate equation (1) and (2) and same for equation (2) and (3) because all of them equal r²

Thus;

(2 - h)² + (-3 - k)² = (4 - h)² + (3 - k)² - - - - - (4)

(4 - h)² + (3 - k)² = (-2 - h)² + (5 - k)² - - - - -(5)

- Simplify (5);

h² - 8h + 16 + k² - 6k + 9 = h² + 4h + 4 + k² - 10k + 25

h² and k² will cancel out to give;

-8h - 6k + 25 = 4h - 10k + 29

Rearranging, we have;

12h - 4k = -4 - - - - (6)

Similarly, for equation 4;

(2 - h)² + (-3 - k)² = (4 - h)² + (3 - k)²

h² - 4h + 4 + k² + 6k + 9 = h² - 8h + 16 + k² - 6k + 9

h², k² and 9 will cancel out to give;

4 - 4h + 6k = 16 - 8h - 6k

Rearranging;

4h + 12k = 12 - - - - (7)

Divide by 4 to give;

h + 3k = 3

Making h the subject;

h = 3 - 3k

Put 3 - 3k for h in eq 6;

12(3 - 3k) - 4k = -4

36 - 36k - 4k = -4

40k = 40

k = 40/40

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2 years ago
A supervisor records the repair cost for 17 randomly selected stereos. A sample mean of $66.34 and standard deviation of $15.22
expeople1 [14]

Answer:

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Step-by-step explanation:

We have the standard deviation for the sample. So we use the t-distribution to solve this question.

The first step to solve this problem is finding how many degrees of freedom, we have. This is the sample size subtracted by 1. So

df = 17 - 1 = 16

80% confidence interval

Now, we have to find a value of T, which is found looking at the t table, with 16 degrees of freedom(y-axis) and a confidence level of 1 - \frac{1 - 0.8}{2} = 0.9. So we have T = 1.337, which is the critical value

The margin of error is:

M = T*s = 1.337*15.22 = 20.349

In which s is the standard deviation of the sample.

The lower end of the interval is the sample mean subtracted by M. So it is 66.34 - 20.349 = $45.991

The upper end of the interval is the sample mean added to M. So it is 66.34 + 20.349 = $86.689

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2 years ago
A baker’s dozen (13) of cookies is on sale for $2.08.
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2 years ago
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