Answer:
A sample size of 385 is needed.
Step-by-step explanation:
We have that to find our
level, that is the subtraction of 1 by the confidence interval divided by 2. So:

Now, we have to find z in the Ztable as such z has a pvalue of
.
That is z with a pvalue of
, so Z = 1.96.
Now, find the margin of error M as such

In which
is the standard deviation of the population and n is the size of the sample.
You feel that a reasonable estimate of the standard deviation is 10.0 hours.
This means that 
What sample size is needed so that the expected margin of error of your estimate is not larger than one hour for 95% confidence?
A sample size of n is needed. n is found when M = 1. So





Rounding up:
A sample size of 385 is needed.
Answer:
b = 3, which is an extraneous solution because if we replace b = 3 in the equation, we must be 5/0 and 30/0, and there is division by 0.
Step-by-step explanation:

The minus common multiply must be (b-3)*(b+3) = b² - 9

7b - 21 + 5b + 15 = 10b
2b = 6
b = 3
Which is an extraneous solution because if we replace b = 3 in the equation, we must be 5/0 and 30/0, and there is division by 0. So this solution is invalid.
Answer:
Rounded to the nearest integer, the company has a total of 82,958 employees.
Step-by-step explanation:
Given that an international company has 25,800 employees in one country, if this represents 31.1% of the companies employees, to determine how many employees does it have in total, the following calculation must be performed:
31.1 = 25,800
100 = X
100 x 25,800 / 31.1 = X
2,580,000 / 31.1 = X
82,958.1 = X
Thus, rounded to the nearest integer, the company has a total of 82,958 employees.
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