Answer:
The standard deviation is 7.7
Step-by-step explanation:
Problems of normally distributed samples can be solved using the z-score formula.
In a set with mean
and standard deviation
, the zscore of a measure X is given by:

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.
In this problem, we have that:

8 percent of the scores are above 89
This means that X = 89 has a pvalue of 1 - 0.08 = 0.92. So when Z = 89, Z = 1.405.





The standard deviation is 7.7
Answer:
I just need points sorry for that
12 songs. 25% of 12 is 3, so you add 3 to 12 and get 15. You then find that 20% of 15 is 3 so you subtract 3 from 15 and get 12 again.
Answer:
6075
Step-by-step explanation:
- Given series is: 25 + 30 + 35 + ⋯ + 245.
- Here, first term (a) = 25
- Common difference (d) = 5
- Last term

- First we find the number of terms that this series has by the following formula:
- Plugging the values of a, d and
, we find.
- Thus, the given series contains 45 terms.
- Next, we find the sum of the given series using the formula given below.