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Marina86 [1]
2 years ago
8

Can someone please help me figure out how to solve for x?​

Mathematics
1 answer:
Anna007 [38]2 years ago
8 0

Answer:

x=30

Step-by-step explanation:

Both triangles in this figure are similar. Therefore, we can set up the following proportion:

\frac{21}{x}=\frac{14}{20}.

Cross-multiply to solve:

14x=21\cdot 20,\\x=\frac{21\cdot20}{14},\\x=\fbox{$30$}.

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Seven ninths as a decimal
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In a survey, the planning value for the population proportion is p* = 0.35. How large a sample should be taken to provide a 95%
lions [1.4K]

Answer:

n=\frac{0.35(1-0.35)}{(\frac{0.05}{1.96})^2}=349.59  

And rounded up we have that n=350  

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".  

p represent the real population proportion of interest

\aht p represent the estimated proportion for the sample

n is the sample size required (variable of interest)

z represent the critical value for the margin of error

Solution to the problem

The population proportion have the following distribution  

p \sim N(p,\sqrt{\frac{\hat p(1-\hat p)}{n}})  

In order to find the critical value we need to take in count that we are finding the interval for a proportion, so on this case we need to use the z distribution. Since our interval is at 95% of confidence, our significance level would be given by \alpha=1-0.95=0.05 and \alpha/2 =0.025. And the critical value would be given by:  

z_{\alpha/2}=-1.96, z_{1-\alpha/2}=1.96  

The margin of error for the proportion interval is given by this formula:  

ME=z_{\alpha/2}\sqrt{\frac{\hat p (1-\hat p)}{n}} (a)  

And on this case we have that ME =\pm 0.05 and we are interested in order to find the value of n, if we solve n from equation (a) we got:  

n=\frac{\hat p (1-\hat p)}{(\frac{ME}{z})^2} (b)

And replacing into equation (b) the values from part a we got:  

n=\frac{0.35(1-0.35)}{(\frac{0.05}{1.96})^2}=349.59  

And rounded up we have that n=350  

6 0
3 years ago
Ada charges a flat rate of $56.00 for painting houses plus an additional $8.00 for each hour she works. Which of the following e
Evgen [1.6K]

Answer:

cost = 56 + 8t, where t is the number of hours worked for.

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Step-by-step explanation:

5 0
3 years ago
I have corner points of:
WARRIOR [948]
The points you found are the vertices of the feasible region. I agree with the first three points you got. However, the last point should be (25/11, 35/11). This point is at the of the intersection of the two lines 8x-y = 15 and 3x+y = 10

So the four vertex points are:
(1,9)
(1,7)
(3,9)
(25/11, 35/11)

Plug each of those points, one at a time, into the objective function z = 7x+2y. The goal is to find the largest value of z

------------------

Plug in (x,y) = (1,9)
z = 7x+2y
z = 7(1)+2(9)
z = 7+18
z = 25
We'll use this value later. 
So let's call it A. Let A = 25

Plug in (x,y) = (1,7)
z = 7x+2y
z = 7(1)+2(7)
z = 7+14
z = 21
Call this value B = 21 so we can refer to it later

Plug in (x,y) = (3,9)
z = 7x+2y
z = 7(3)+2(9)
z = 21+18
z = 39
Let C = 39 so we can use it later

Finally, plug in (x,y) = (25/11, 35/11)
z = 7x+2y
z = 7(25/11)+2(35/11)
z = 175/11 + 70/11
z = 245/11
z = 22.2727 which is approximate
Let D = 22.2727

------------------

In summary, we found
A = 25
B = 21
C = 39
D = 22.2727

The value C = 39 is the largest of the four results. This value corresponded to (x,y) = (3,9)

Therefore the max value of z is z = 39 and it happens when (x,y) = (3,9)

------------------

Final Answer: 39

7 0
3 years ago
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