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IB maths normal distribution question

hey guyssss, i need some help please?

4a. Applicants for a job had to complete a mathematics test. The time they took to complete the test is normally distributed with a mean of 53 minutes and a standard deviation of 16.3. One of the applicants is chosen at random.
Find the probability that this applicant took at least 40 minutes to complete the test. (2 marks)

i think it's 0.787 (3sf).

4b. For 11% of the applicants it took longer than k minutes to complete the test. Find the value of k. (2 marks)

4c. There were 400 applicants for the job. Estimate the number of applicants who completed the test in less than 25 minutes. (2 marks)

I got 64 applicants but not sure...

(@JackMoseley ?)

(edited 4 years ago)