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3 years ago

Mr. Lincoln buys juice and water for the school picnic. A pack of 8 juice boxes ca

Mathematics

1 answer:

alexgriva [62]3 years ago

4 0

Answer:

5x + 3y = 95

8x + 6y = 170

x = 10 ; y = 15

Step-by-step explanation:

Let :

x = pack of juice boxes

y = pack of water bottles

Pack of juice box = $5

Pack of water bottles = $3

Amount of money spent :

5x + 3y = $95

Number of drinks purchased :

8x + 6y = 170

Using both equations ;

5x + 3y = 95 - - - (1)

8x + 6y = 170 - - - (2)

Multiply (1) by 6 and (2) by 3

30x + 18y = 570

24x + 18y = 510

Subtract :

6x = 60

x = 60 / 6

x = 10

Put x = 10 in (1)

5(10) + 3y = 95

50 + 3y = 95

3y = 95 - 50

3y = 45

y = 45 / 3

y = 15

x = 10 ; y = 15

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2 years ago

A random sample of 9 wheels of cheese yielded the following weights in pounds has a sample mean of 20.90 and a sample variance o

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Answer:

$2.002 \leq \sigma^2 \leq 11.365$

Step-by-step explanation:

1) Data given and notation

s represent the sample standard deviation

$s^2$ represent the sample variance

n=9 the sample size

Confidence=90% or 0.90

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 mean or variance 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.

The Chi Square distribution is the distribution of the sum of squared standard normal deviates .

2) Calculating the confidence interval

The confidence interval for the population variance is given by the following formula:

$\frac{(n-1)s^2}{\chi^2_{\alpha/2}} \leq \sigma \frac{(n-1)s^2}{\chi^2_{1-\alpha/2}}$

On this case we need to find the sample standard deviation with the following formula:

$s=sqrt{\frac{\sum_{i=1}^9 (x_i -\bar x)^2}{n-1}}
The sample variance given was [tex]s^2=3.45$

The next step would be calculate the critical values. First we need to calculate the degrees of freedom given by:

$df=n-1=9-1=8$

Since the Confidence is 0.90 or 90%, the value of $\alpha=0.1$ and $\alpha/2 =0.05$ , and we can use excel, a calculator or a table to find the critical values.