Answer:
A sample of 499 is needed.
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 given by:
In this question, we have that:
90% confidence level
So 
, z is the value of Z that has a pvalue of 
, so 
.
How large a sample would be required in order to estimate the fraction of tenth graders reading at or below the eighth grade level at the 90% confidence level with an error of at most 0.03
We need a sample of n, which is found when 
. So
Rounding up
A sample of 499 is needed.
Answer:
D
Step-by-step explanation:
First, find the 40% discount.
40% of 195 is 78
195 x 0.40 = 78
Subtract that from 195
195 - 78 = 117
Now, find 66 2/3% of 117, since it is an additional reduction after the original discount.
2/3 = 0.667, so 66 2/3% is 66.667%
117 x 0.66667 = 78.00039
And subtract that from 117
117 - 78.00039 = 38.99961, which in dollars would be $38.99. (hundredths, etc. of a cent are usually just dropped; no rounding involved.)
The discount price would then be $38.99
