(b) A car repair shop uses a particular spare part at an average rate of 6 per week. Find the probability that: i. at least 6 are used in a particular week. ii. exactly 18 are used in a 3-week period. iii. exactly 6 are used in each of 3 successive weeks.

A First Course in Probability (10th Edition)
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Chapter1: Combinatorial Analysis
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Problem 1.1P: a. How many different 7-place license plates are possible if the first 2 places are for letters and...
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3. (a) Susan tries to exercise at "Pure Fit" Gym each day of the week, except on the weekends
(Saturdays and Sundays). Susan is able to exercise, on average, on 75% of the weekdays
(Monday to Friday).
i. Find the expected value and the standard deviation of the number of days she
exercises in a given week.
ii. Given that Susan exercises on Monday, find the probability that she will exercise at
least 3 days in the rest of the week.
iii. Find the probability that in a period of four weeks, Susan exercises 3 or less days in
only two of the four weeks.
(b) A car repair shop uses a particular spare part at an average rate of 6 per week. Find the
probability that:
i. at least 6 are used in a particular week.
ii. exactly 18 are used in a 3-week period.
iii. exactly 6 are used in each of 3 successive weeks.
(c) The breaking strength (in pounds) of a certain new synthetic piece of glass is normally
distributed, with a mean of 115 pounds and a variance of 4 pounds.
i. What is the probability that a single randomly selected piece of glass will have
breaking strength between 118 and 120 pounds?
ii. A new synthetic piece of glass is considered defective if the breaking strength is less
than 113.6 pounds. What is the probability that a single randomly selected piece of
glass will be defective?
iii. What is the probability that out of 200 pieces of randomly selected glass, more than
fifty-five of them are defective.
Transcribed Image Text:3. (a) Susan tries to exercise at "Pure Fit" Gym each day of the week, except on the weekends (Saturdays and Sundays). Susan is able to exercise, on average, on 75% of the weekdays (Monday to Friday). i. Find the expected value and the standard deviation of the number of days she exercises in a given week. ii. Given that Susan exercises on Monday, find the probability that she will exercise at least 3 days in the rest of the week. iii. Find the probability that in a period of four weeks, Susan exercises 3 or less days in only two of the four weeks. (b) A car repair shop uses a particular spare part at an average rate of 6 per week. Find the probability that: i. at least 6 are used in a particular week. ii. exactly 18 are used in a 3-week period. iii. exactly 6 are used in each of 3 successive weeks. (c) The breaking strength (in pounds) of a certain new synthetic piece of glass is normally distributed, with a mean of 115 pounds and a variance of 4 pounds. i. What is the probability that a single randomly selected piece of glass will have breaking strength between 118 and 120 pounds? ii. A new synthetic piece of glass is considered defective if the breaking strength is less than 113.6 pounds. What is the probability that a single randomly selected piece of glass will be defective? iii. What is the probability that out of 200 pieces of randomly selected glass, more than fifty-five of them are defective.
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