If 3, x, y, -9 are in A.P, find the values of x and y.

Mathematics

1 answer:

Serggg [28]2 years ago

6 0

Answer:

x = -1
y = -5

Step-by-step explanation:

The common difference (d) can be found using the first and 4th terms:

a1 = 3

a4 = a1 +d(4 -1)

-9 = 3 +3d . . . . . simplify

-3 = 1 + d . . . . . . divide by 3

-4 = d . . . . . . . . . subtract 1

Then ...

x = a1 + d = 3 -4 = -1

y = x + d = -1 -4 = -5

The values of x and y are -1 and -5, respectively.

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The manager of a grocery store has taken a random sample of 100 customers. The average length of time it took these 100 customer

AlladinOne [14]

Answer:

$4-2.326\frac{1}{\sqrt{100}}=3.767$

$4+2.326\frac{1}{\sqrt{100}}=4.233$

So on this case the 98% confidence interval would be given by (3.767;4.233)

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".

$\bar X=4$ represent the sample mean

$\mu$ population mean (variable of interest)

$\sigma=1$ represent the population standard deviation

n=100 represent the sample size

Solution to the problem

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 0.98 or 98%, the value of $\alpha=0.02$ and $\alpha/2 =0.01$ , and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-NORM.INV(0.01,0,1)".And we see that $z_{\alpha/2}=2.326$