The time that it takes for the next train to come follows a distribution with f(x) = 0.05 where x goes between 15 and 35 minutes. Round all numerical answers to two decimal places.

Answers:

a) mean = 2

b) Standard Deviation = 5.77

c) Probability that it takes 30 minutes for the next train to arrive = 0.75

d) Probability that the time taken will be between 25 and 30 minutes = 0.25

e) The 80th percentile = 31 minutes

f) The third quartile = 30 minutes

Explanations:

Check the attached files for the solvings

walter needs to make at least 5 more cookies but no more than 40. 5 ≤ x ≤ 40

step-by-step explanation:

20 ≤ x + 15 ≤ 55

subtract 15 from all parts

20-15 ≤ x + 15-15 ≤ 55-15

5 ≤ x ≤ 40

this means how many more cookies he has to make

walter needs to make at least 5 more cookies, but no more than 40 cookies; 5 ≤ x ≤ 40