Answer:
29.2
Step-by-step explanation:
Mean = 21.4
Standard deviation = 5.9%
The minimum score required for the scholarship which is the scores of the top 9% is calculated using the Z - Score Formula.
The Z- score formula is given as:
z = x - μ /σ
Z score ( z) is determined by checking the z score percentile of the normal distribution
In the question we are told that it is the students who scores are in the top 9%
The top 9% is determined by finding the z score of the 91st percentile on the normal distribution
z score of the 91st percentile = 1.341
Using the formula
z = x - μ /σ
Where
z = z score of the 91st percentile = 1.341
μ = mean = 21.4
σ = Standard deviation = 5.9
1.341= x - 21.4 / 5.9
Cross multiply
1.341 × 5.9 = x - 21.4
7.7526 = x -21.4
x = 7.7526 + 21.4
x = 29.1526
The 91st percentile is at the score of 29.1526.
We were asked in the question to round up to the nearest tenth.
Approximately, = 29.2
Step-by-step explanation:
5 nail polish and 4 lip gloss
5 x 4.5 =22.5
4 x 7 =28
28+22.5=50.50
We have been given for a normal distribution the mean time it takes to walk to the bus stop is 8 minutes with a standard deviation of 2 minutes. And the mean time it takes for the bus to get to school is 20 minutes with a standard deviation of 4 minutes.
(a) Average time that it would take reach school can be obtained by adding the average times.
8+20 = 28 minutes.
(b) Standard deviation of the trip to school can be found as:

Therefore, standard deviation of the entire trip is 4.47 minutes.
(c) Let us first find z score corresponding to 30 minutes.
We need to find the probability such that 
Therefore, the required probability is 0.67.
(d) If average time to walk to school is 10 minutes, then overall average time for the trip will be 10+20 = 30 minutes.
(e) Standard deviation won't change it will remain 4.47
(f) The new probability will be:


Therefore, probability will be 0.50.