Rewrite the expression by factoring out (x-8)

Given that 1 inch =2.54 Gm how many centimeters are there in 4 feet?

frutty [35]

Answer:

121.92

Step-by-step explanation:

There's 121.92 centimeters in 4 feet.

Hope this helps! :^)

7 0

3 years ago

In a recent study of 35 ninth-grade students, the mean number of hours per week that they played video games was 16.6. The stand

Mariulka [41]

Answer:

a) 16.6

b) The 95% confidence level of the mean of the time playing video games is between 15.7 and 17.5 hours.

c) The 99% confidence level of the mean of the time playing video games is between 15.4 and 17.8 hours.

d) The margin of error increases as the confidence level increases, due to the value of z, which means that the 99% confidence interval is larger.

Step-by-step explanation:

a. Find the best point of estimate of the population mean

The best estimate for the population mean is the sample mean, which is 16.6

b. Find the 95% confidence level of the mean of the time playing video games

We have that to find our $\alpha$ level, that is the subtraction of 1 by the confidence interval divided by 2. So:

$\alpha = \frac{1 - 0.95}{2} = 0.025$

Now, we have to find z in the Ztable as such z has a pvalue of $1 - \alpha$ .

That is z with a pvalue of $1 - 0.025 = 0.975$ , so Z = 1.96.

Now, find the margin of error M as such

$M = z\frac{\sigma}{\sqrt{n}}$

In which $\sigma$ is the standard deviation of the population and n is the size of the sample.

$M = 1.96\frac{2.8}{\sqrt{35}} = 0.9$

The lower end of the interval is the sample mean subtracted by M. So it is 16.6 - 0.9 = 15.7 hours

The upper end of the interval is the sample mean added to M. So it is 16.6 - 0.9 = 17.5 hours

The 95% confidence level of the mean of the time playing video games is between 15.7 and 17.5 hours.

c. Find the 99% confidence interval of the mean time playing video games

Following the same logic as above, we have that $Z = 2.575$ . So

$M = 2.575\frac{2.8}{\sqrt{35}} = 0.9$

The lower end of the interval is the sample mean subtracted by M. So it is 16.6 - 1.2 = 15.4 hours.

The upper end of the interval is the sample mean added to M. So it is 16.6 + 1.2 = 17.8 hours.

The 99% confidence level of the mean of the time playing video games is between 15.4 and 17.8 hours.

d. Which is larger? Explain why.

The margin of error increases as the confidence level increases, due to the value of z, which means that the 99% confidence interval is larger.

5 0

3 years ago

Bob the builder is making 480kg of concrete mix

vichka [17]

To answer this item, we are first to determine the common factor between the amounts of the cement, sand, and gravel.

If we let x be this factor, the amount of the cement would be x. Similarly, the amount of sand is 3x, and lastly the amount of gravel is 4x. Then, we establish the equation that would let us relate the amounts.

x + 3x + 4x = 480

Simplifying,

8x = 480

x = 60

Hence, the amount of cement is 60 kg, that of sand is 180 kg. Lastly, the amount of gravel is 240 kg.

5 0

3 years ago

Let x represent the number of batteries and y represent the cost of the batteries. A package of 8 rechargeable batteries costs $

Rasek [7]

Answer:

8 battery =12

20 battery =?(x)

8x=240

x=240÷8

x=30

for 20 battery..it would cost 30

Step-by-step explanation:

5 0

3 years ago

What is the reciprocal of -2/5

AysviL [449]

Answer:

5/-2

Step-by-step explanation:

The reciprocal of a fraction is simply the original fraction flipped.

6 0

3 years ago