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2 years ago

A circle with area 100π has a sector with a central angle of 2/5π radians.

Mathematics

1 answer:

Snowcat [4.5K]2 years ago

3 0

Answer:

20π square units

Step-by-step explanation:

The sector area is found using the proportion ...

sector area / circle area = sector angle / whole circle angle

Multiplying by "circle area", we get ...

sector area = (circle area)( sector angle / whole circle angle)

= (100π)(2/5π)/(2π)

= (100π)(1/5)

sector area = 20π

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A researcher wishes to estimate the percentage of adults who support abolishing the penny. What size sample should be obtained i

Scorpion4ik [409]

Answer:

a) We need a sample size of at least 3109.

b) We need a sample size of at least 4145.

Step-by-step explanation:

In a sample with a number n of people surveyed with a probability of a success of $\pi$ , and a confidence level of $1-\alpha$ , we have the following confidence interval of proportions.

$\pi \pm z\sqrt{\frac{\pi(1-\pi)}{n}}$

In which

z is the zscore that has a pvalue of $1 - \frac{\alpha}{2}$ .

The margin of error is:

$M = z\sqrt{\frac{\pi(1-\pi)}{n}}$

99% confidence level

So $\alpha = 0.01$ , z is the value of Z that has a pvalue of $1 - \frac{0.01}{2} = 0.995$ , so $Z = 2.575$ .

(a) he uses a previous estimate of 25%?

we need a sample of size at least n.

n is found when $M = 0.02, \pi = 0.25$ . So

$M = z\sqrt{\frac{\pi(1-\pi)}{n}}$

$0.02 = 2.575\sqrt{\frac{0.25*0.75}{n}}$

$0.02\sqrt{n} = 2.575\sqrt{0.25*0.75}$

$\sqrt{n} = \frac{2.575\sqrt{0.25*0.75}}{0.02}$

$(\sqrt{n})^{2} = (\frac{2.575\sqrt{0.25*0.75}}{0.02})^{2}$

$n = 3108.1$

We need a sample size of at least 3109.

(b) he does not use any prior estimates?

When we do not use any prior estimate, we use $\pi = 0.5$

$M = z\sqrt{\frac{\pi(1-\pi)}{n}}$

$0.02 = 2.575\sqrt{\frac{0.5*0.5}{n}}$

$0.02\sqrt{n} = 2.575\sqrt{0.5*0.5}$

$\sqrt{n} = \frac{2.575\sqrt{0.5*0.5}}{0.02}$

$(\sqrt{n})^{2} = (\frac{2.575\sqrt{0.5*0.5}}{0.02})^{2}$

$n = 4144.1$

Rounding up

We need a sample size of at least 4145.

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3 years ago

Santiago collects 435 cents in nickels.how many nickels does he collect?

Marianna [84]

He has 87 nickels (divide 435 by 5).

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3 years ago

Sara can finish 5 laps around the track in 6 minutes. What is her average speed in miles per hour, if it takes 12 laps around th

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Answer:

4 1/6 miles per hour

Step-by-step explanation:

6 minutes is 1/10 hour, so Sara's speed is ...

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Sara's speed is 4 1/6 miles per hour.

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2 years ago

I eat 2 spoons of nuts every day for a week. Then I eat 3 spoons for the following w weeks. How many spoons did I eat on average

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Answer:

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3 years ago

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Below is the solution:

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3 years ago