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kkurt [141]
3 years ago
6

I need help with 19, 20, and 21! please and thank you!

Mathematics
1 answer:
Tom [10]3 years ago
6 0
19) because 1/2 an hour is 8 miles, 1 hour will take 16 miles , multiply 8 by 2 because I️t gave half an hour so multiplying by 2 will give an hour (2 half’s make a whole)

20) 2 1/2 multiplied by 4 is 10, so his jog will be 10 minutes longer

21) 4,500 was what he earned and 4,900 was what he lost (“expenses”) so he lost $400:
$4,500 - $4,900= -$400
He lost money because the answer is negative
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PLZ HELP ME, I'M DOING A TEST I NEED HELP PLZ
Veronika [31]

Answer:

I think its c

Step-by-step explanation:

3 0
3 years ago
An SRS of 350 high school seniors gained an average of x¯=21 points in their second attempt at the SAT Mathematics exam. Assume
Lynna [10]

Answer:

a) 21-2.58\frac{52}{\sqrt{350}}=13.83  

21+2.58\frac{52}{\sqrt{350}}=28.17  

So on this case the 99% confidence interval would be given by (13.83;28.17)  

b) ME=2.58\frac{52}{\sqrt{350}}=7.17

c) ME=2.58\frac{52}{\sqrt{100}}=13.42

d) D. Decreasing the sample size increases the margin of error, provided the confidence level and population standard deviation remain the same.

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".  

Part a

\bar X=21 represent the sample mean  

\mu population mean (variable of interest)  

\sigma=52 represent the population standard deviation  

n=350 represent the sample size  

99% confidence interval  

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

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

Since the Confidence is 0.99 or 99%, the value of \alpha=0.01 and \alpha/2 =0.005, and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-NORM.INV(0.005,0,1)".And we see that z_{\alpha/2}=2.58  

Now we have everything in order to replace into formula (1):  

21-2.58\frac{52}{\sqrt{350}}=13.83  

21+2.58\frac{52}{\sqrt{350}}=28.17  

So on this case the 99% confidence interval would be given by (13.83;28.17)  

Part b

The margin of error is given by:

ME=2.58\frac{52}{\sqrt{350}}=7.17

Part c

The margin of error is given by:

ME=2.58\frac{52}{\sqrt{100}}=13.42

Part d

As we can see when we reduce the sample size we increase the margin of error so the best option for this case is:

D. Decreasing the sample size increases the margin of error, provided the confidence level and population standard deviation remain the same.

6 0
3 years ago
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Kryger [21]

Answer:

64x²y²

Step-by-step explanation:

Use the great smart calculator

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8 0
2 years ago
5/6 of 15 i need help????????????
emmainna [20.7K]

Answer: 12.5 or 12 1/2

Step-by-step explanation:

7 0
3 years ago
Read 2 more answers
Math help please? There are 12 more toy cars than toy trucks in a box with a total of 38 toy cars and toy trucks. How many toy t
dlinn [17]
Let, the number of toy trucks = x
Then, number of toy cars = (x + 12)

Now, we have: x + x+12 = 38
2x + 12 = 38
2x = 38 - 12
2x = 26
x = 26/2
x = 13

So, there are 13 toy trucks in total.

Hope this helps!
7 0
3 years ago
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