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Aleks04 [339]
3 years ago
11

It takes 20 minutes for 5people to paint 5 walls. How many minutes does it take 9 people to paint 9walls?

Mathematics
1 answer:
juin [17]3 years ago
8 0

Answer:

20 minutes.

Step-by-step explanation:

Since it takes 5 people to paint 5 walls 20 minutes, that means that it would take 1 person 20 minutes to paint 1 wall. That also means that 2 people would take 20 minutes to paint 2 walls. So, it would take 9 people 20 minutes to paint 9 walls.

Hope this helps!

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In a random sample of 80 teenagers, the average number of texts handled in a day is 50. The 96% confidence interval for the mean
Nastasia [14]

Answer:

a) \bar X =\frac{46+54}{2}=50

And the margin of error is given by:

ME= \frac{54-46}{2}= 4

The confidence level is 0.96 and the significance level is \alpha=1-0.96=0.04 and the value of \alpha/2 =0.02 and the margin of error is given by:

ME=z_{\alpha/2}\frac{\sigma}{\sqrt{n}}

We can calculate the critical value and we got:

z_{\alpha/2} = 2.05

And if we solve for the deviation like this:

\sigma = ME * \frac{\sqrt{n}}{z_{\alpha/2}}

And replacing we got:

\sigma =4 *\frac{\sqrt{80}}{2.05} =17.45

b) ME=z_{\alpha/2}\frac{\sigma}{\sqrt{n}}=2.05 *\frac{17.45}{\sqrt{160}}=2.828

And as we can see that the margin of error would be lower than the original value of 4, the margin of error would be reduced by a factor \sqrt{2}

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".  

\bar X represent the sample mean  

\mu population mean (variable of interest)  

\sigma represent the population standard deviation  

n=80 represent the sample size  

Solution to the problem

Part a

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

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

For this case we can calculate the mean like this:

\bar X =\frac{46+54}{2}=50

And the margin of error is given by:

ME= \frac{54-46}{2}= 4

The confidence level is 0.96 and the significance level is \alpha=1-0.96=0.04 and the value of \alpha/2 =0.02 and the margin of error is given by:

ME=z_{\alpha/2}\frac{\sigma}{\sqrt{n}}

We can calculate the critical value and we got:

z_{\alpha/2} = 2.05

And if we solve for the deviation like this:

\sigma = ME * \frac{\sqrt{n}}{z_{\alpha/2}}

And replacing we got:

\sigma =4 *\frac{\sqrt{80}}{2.05} =17.45

Part b

For this case is the sample size is doubled the margin of error would be:

ME=z_{\alpha/2}\frac{\sigma}{\sqrt{n}}=2.05 *\frac{17.45}{\sqrt{160}}=2.828

And as we can see that the margin of error would be lower than the original value of 4, the margin of error would be reduced by a factor \sqrt{2}

5 0
2 years ago
Evaluate 3a2 + 4b2 for a =<br> 2 and b = 3.<br> O<br> 168<br> 48<br> O<br> 36
Juliette [100K]

Answer:

48

Step-by-step explanation:

a=2

b=3

3a^2+4b^2

3(2)^2+4(3)^2

3(2)(2)+4(3)(3)

3(4)+4(9)

12+36

48

Hope this helps ;) ❤❤❤

8 0
2 years ago
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Salsk061 [2.6K]

Answer:

= -3(x+3)x(2x-1)

Step-by-step explanation:

5 0
3 years ago
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What is the volume of a cone (in cubic inches) of radius 5 inches and height 3
beks73 [17]

Answer:

78.54 cm^3

Step-by-step explanation:

I think thats the answer

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3 years ago
Just having one part does not make the triangles
12345 [234]

Answer: True.

Step-by-step explanation:

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