Numerade

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Christopher Dzorkpata

Numerade educator

A bag contains 3 red balls and 2 blue balls. i) If two balls were drawn at random one at a time with replacement. What is the probability that the first one is red and the second one is blue? Ans:6/25 ii) If two balls were drawn at random one at a time without replace- ment. What is the probability that the first one is red and the second one is blue? Ans: 3/10

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Umar Sohail Qureshi

Numerade educator

Suppose that 30% of all students who have to buy a text for a particular course want a new copy (the successes!), whereas the other 70% want a used copy. Consider randomly selecting 15 purchasers. (a) What are the mean value and standard deviation of the number who want a new copy of the book? (b) What is the probability that the number who want new copies is more than two standard deviations away from the mean value? (c) The bookstore has 10 new copies and 10 used copies in stock. If 15 people come in one by one to purchase this text, what is the probability that all 15 will get the type of book they want from current stock? [Hint: Let X = the number who want a new copy. For what values of X will all 15 get what they want?] (d) Suppose that new copies cost $140 and used copies cost $60. Assume the bookstore currently has 50 new copies and 50 used copies. What is the expected value of total revenue from the sale of the next 15 copies purchased? [Hint: Let h(X) = the revenue when X of the 15 purchasers want new copies. Express this as a linear function.]

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Umar Sohail Qureshi

Numerade educator

A box in a supply room contains compact fluorescent lightbulbs, of which 5 are rated 13-watt, 6 are rated 18-watt, and 4 are rated 23-watt. Suppose that three of these bulbs are randomly selected. a) What is the probability that exactly two of the selected bulbs are rated 23-watt? b) What is the probability that all three of the bulbs have the same rating? c) What is the probability that one bulb of each type is selected? d) If bulbs are selected one by one until a 23-watt bulb is obtained, what is the probability that it is necessary to examine at least 6 bulbs?

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Wilfredo Molina

Numerade educator

A bag contains 3 red balls and 2 blue balls. i) If two balls were drawn at random one at a time with replacement. What is the probability that the first one is red and the second one is blue? ii) If two balls were drawn at random one at a time without replace- ment. What is the probability that the first one is red and the second one is blue?

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Emmanuel G.