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Vinvika [58]
2 years ago
13

Plzzz helppp giving brainiest to the first one

Mathematics
2 answers:
Monica [59]2 years ago
8 0

Answer:

I’m smart UwU

Step-by-step explanation:

aniked [119]2 years ago
4 0

Answer:

Arsenic-74-is used to locate brain tumors. It has a half-life of 17.5 days. ... C. Find the amount remaining after 6 days from a 90-mg sample

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X/1.5 = 4*<br> Help me plz
Anna11 [10]

Answer:

x = 6

Step-by-step explanation:

\frac{x}{1.5} =4\\\\

We can multiply both sides by 1.5 to isolate x

x=4*1.5\\x=6

4 0
2 years ago
Read 2 more answers
What is 6+ -5 2/3 in fraction form
aleksklad [387]

Answer:

1/3

Step-by-step explanation:

6+-5 2/3 = 6-5 2/3, so the difference is 1/3

6 0
2 years ago
You want to obtain a sample to estimate a population proportion. At this point in time, you have no reasonable estimate for the
Vesna [10]

Answer:

A sample size of at least 1,353,733 is required.

Step-by-step explanation:

In a sample with a number n of people surveyed with a probability of a success of , and a confidence level of , 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 .

The margin of error is:

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

98% confidence level

So \alpha = 0.02, z is the value of Z that has a pvalue of 1 - \frac{0.02}{2} = 0.99, so Z = 2.327.  

You would like to be 98% confident that you esimate is within 0.1% of the true population proportion. How large of a sample size is required?

We need a sample size of at least n.

n is found when M = 0.001.

Since we don't have an estimate for the proportion, we use the worst case scenario, that is \pi = 0.5

So

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

0.001 = 2.327\sqrt{\frac{0.5*0.5}{n}}

0.001\sqrt{n} = 2.327*0.5

\sqrt{n} = \frac{2.327*0.5}{0.001}

(\sqrt{n})^{2} = (\frac{2.327*0.5}{0.001})^{2}

n = 1353732.25

Rounding up

A sample size of at least 1,353,733 is required.

5 0
3 years ago
A study was designed to investigate the effects of two​ variables, (1) A​ student's level of mathematical anxiety and​ (2) teach
Mashcka [7]

Answer:

P(X>400)=P(\frac{X-\mu}{\sigma}>\frac{400-\mu}{\sigma})=P(Z>\frac{400-440}{20})=P(z>-2)

And we can find this probability using the complement rule:

P(z>-2)=1-P(z

And in order to find these probabilities we can find tables for the normal standard distribution, excel or a calculator.  

P(z>-2)=1-P(z

Step-by-step explanation:

Previous concepts

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".

The Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".  

Solution to the problem

Let X the random variable that represent the scores of a population, and for this case we know the distribution for X is given by:

X \sim N(440,20)  

Where \mu=440 and \sigma=20

We are interested on this probability

P(X>440)

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

z=\frac{x-\mu}{\sigma}

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

P(X>400)=P(\frac{X-\mu}{\sigma}>\frac{400-\mu}{\sigma})=P(Z>\frac{400-440}{20})=P(z>-2)

And we can find this probability using the complement rule:

P(z>-2)=1-P(z

And in order to find these probabilities we can find tables for the normal standard distribution, excel or a calculator.  

P(z>-2)=1-P(z

6 0
3 years ago
Haley has enlarged a 3-inch by 5-inch picture so that both the length and width are tripled. The area of the enlarged photo is h
77julia77 [94]

Answer:

9 times

Step-by-step explanation:

Area = length x breadth

area of picture not enlarged = 3 x 5 = 15in²

If length is tripled it becomes , 3 x 3 = 9in

If width is tripled, it becomes , 5 x 3 = 15in

Area of enlarged picture = 9in x 15in = 135in²

amount by which enlarged image is larger = 135in² /15in² = 9

5 0
2 years ago
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