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You need 320 mL of a 85% alcohol solution. On hand, you have a 60% alcohol mixture. How much of the 60% alcohol mixture and pure

Radda [10]

Answer:

Step-by-step explanation:

If we let x = the amount of 5% solution and y = the amount of pure alcohol, we can set up that

.05x+y is the amount of alcohol in our resulting mixture, and x+y is the total amount in our resulting mixture (which we know is 380)

so we also know that:

(.05x+y)/380 = .6

If we simplify this we come up with:

.05x+y=228

and we know x+y=380

If we solve this as a system of equations, we will find that:

x=160 ml

y=220 ml

5 0

3 years ago

Pls help it’s pretty easy

lutik1710 [3]

Answer:

x = 0.5

Step-by-step explanation:

3 0

3 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 $z_{\alpha/2}=2.58$