Answer:
The required sample size for the new study is 801.
Step-by-step explanation:
In a sample with a number n of people surveyed with a probability of a success of
, and a confidence level of
, we have the following confidence interval of proportions.

In which
z is the zscore that has a pvalue of
.
The margin of error is:

25% of all adults had used the Internet for such a purpose
This means that 
95% confidence level
So
, z is the value of Z that has a pvalue of
, so
.
What is the required sample size for the new study?
This is n for which M = 0.03. So






Rounding up:
The required sample size for the new study is 801.
Multiply the first equation by 2
2x + 2y =30
now we’ll add the second equation to the first equation
2x + 2y =30
-2x+5y= -2
7y=28
divide by 7
y=4
now plug y back into the first equation
x + 4 = 15
subtract 4
x=11
8 x 5 = 40
40 x 18 = 720
Hope this helps!
Answer:
4%
Step-by-step explanation:
After losing 4.17, it came down to 100.08, so the opening price was:
100.08 + 4.17 = 104.25
To find percentage decline, we find the ratio of the "change" (which is 4.17) divided by the opening (original) price, which is 104.25. Then we multiply that fraction by 100 to get our percentage decline.
So,

Thus, the
percentage decline = 4%