David was thinking of a number. David doubles it and adds 2.9 to get an answer of 13.2. Form an equation with

Can some one help me with this question its hard :( down below ill give brainliest

vredina [299]

Answer:

C. 1

Step-by-step explanation:

I got this right on my test

7 0

3 years ago

The population in the town of Huntersville is presently 38,300. The town grows at an annual rate of 1.2%. Find the population of

Basile [38]

Hi there! So the situation that we are talking about for this is compounding, because the population is growing.. The formula for compounding something is P(1 + r)^t, with P representing the initial amount, r representing the rate, and t representing the time in years. First off, let's add the rate into 1. 1.2% is 0.012 in decimal form. 1 + 0.012 is 1.012. Now, because we are looking for the population after 4 years. We raise 1.012 to the 4th power. 1.012^4 is 1.04887093274. It's a long decimal, but do not delete this number from your calculator. Now, we multiply that number by 38,300 in order to get 40,171.7567238 or 40,172 when rounded to the nearest whole number. There. The population of Huntersville will be 40,172 people in 4 years.

3 0

3 years ago

Show that cos2x=cosx

PSYCHO15rus [73]

cos (2x) = cos x

2 cos^2 x -1 = cos x using the double angle formula

2 cos ^2 x -cos x -1 =0

factor

(2 cos x+1) ( cos x -1) = 0

using the zero product property

2 cos x+1 =0 cos x -1 =0

2 cos x = -1 cos x =1

cos x = -1/2 cos x=1

taking the arccos of each side

arccos cos x = arccos (-1/2) arccos cos x = arccos 1

x = 120 degrees x=-120 degrees x=0

remember you get 2 values ( 2nd and 3rd quadrant)

these are the principal values

now we need to add 360

x = 120+ 360n x=-120+ 360n x = 0 + 360n where n is an integer

3 0

3 years ago

What is 18=j+4 plz help

Thepotemich [5.8K]

Answer:

Hope this helps

Step-by-step explanation:

j=14

3 0

2 years ago

Read 2 more answers

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