I’M MARKING BRAINLIEST!!!! I really need a good score pls help!

Lena purchased a prepaid phone card for $20. Long distance calls cost 21 cents a minute using this card, Lena used her card only

slega [8]

Answer:

37 minutes

Step-by-step explanation:

Lena has 20 dollars. 20 - 12.23 = 7.77

Lena has $7.77 dollars left.

We divide this by .21 to see how many minutes her call was.

7.77 ÷ .21 = 37

Rate as Brainliest and Thanks plz

5 0

3 years ago

In Applied Life Data Analysis (Wiley, 1982), Wayne Nelson presents the breakdown time of an insulating fluid between electrodes

ale4655 [162]

Answer:

The sample mean is $\bar{x}=14.371$ min.

The sample standard deviation is $\sigma = 18.889$ min.

Step-by-step explanation:

We have the following data set:

$\begin{array}{cccccccc}0.15&0.82&0.81&1.44&2.70&3.28&4.00&4.70\\4.96&6.49&7.25&8.03&8.40&12.15&31.89&32.47\\33.79&36.80&72.92&&&&&\end{array}$

The mean of a data set is commonly known as the average. You find the mean by taking the sum of all the data values and dividing that sum by the total number of data values.

The formula for the mean of a sample is

$\bar{x} = \frac{{\sum}x}{n}$

where, $n$ is the number of values in the data set.

$\bar{x}=\frac{0.15+0.82+0.81+1.44+2.7+3.28+4+4.7+4.96+6.49+7.25+8.03+8.4+12.15+31.89+32.47+33.79+36.80+72.92}{19}\\\\\bar{x}=14.371$

The standard deviation measures how close the set of data is to the mean value of the data set. If data set have high standard deviation than the values are spread out very much. If data set have small standard deviation the data points are very close to the mean.

To find standard deviation we use the following formula

$\sigma = \sqrt{ \frac{ \sum{\left(x_i - \overline{x}\right)^2 }}{n-1} }$

The mean of a sample is $\bar{x}=14.371$ .

Create the below table.

Find the sum of numbers in the last column to get.

$\sum{\left(x_i - \overline{X}\right)^2} = 6422.0982$

$\sigma = \sqrt{ \frac{ \sum{\left(x_i - \overline{x}\right)^2 }}{n-1} } = \sqrt{ \frac{ 6422.0982 }{ 19 - 1} } \approx 18.889$

7 0

3 years ago

Leanne runs on the treadmill and rides the exercise bike at the gym to stay in shape. She burns 15 calories per minute on the tr

sergiy2304 [10]

Answer: C.

Explanation: i just took it. and got a 100. :)

8 0

2 years ago

Free points u guys can have them

sertanlavr [38]

Hi thank u vvv much i am currently failing my bio class and in need of help

7 0

3 years ago

Read 2 more answers

The sum of two numbers is 30. the first number is twice the second number. what are the numbers?

Fudgin [204]

Let the numbers be x and y.

by the first statement of the question, we get , x + y = 30.,,..(1)

by the second satement, we get , x = y+ y => x=2y... (2)

from equation (2), let us put the value of x in equation (1),
x + y = 30
=> 2y + y = 30
=> 3y = 30
=> y =30/3
=> y = 10

and x=2y => x = 2*10 = 20

in short, the numbers are 10 and 20

3 0

3 years ago