B) That 6 Shells Will Be Good and 2 Will Not Fire?

MATH 1101 7.6 Notes

Ex 1: A psychologist claims she can teach four-year-old children to spell three-letter words very quickly. To test her, one of her students was given cards with the letters A, C, D, K, and T on them and told to spell CAT. What is the probability the child will spell CAT by chance?

Ex 2: Suppose that a state issues license plates with three letters formed by three digits and that there are 12 thre-letter words that are not permitted on license plates. If all possible plates are produced and a plate is selected at random, what is the probability that the plate is unacceptable and will not be issued?

Ex 3: A box of 24 shotgun shells contains 4 shells that will not fire. If 8 shells are selected from the box, what is the probability… a) that all 8 shells will be good?

b) that 6 shells will be good and 2 will not fire?

Ex 4: A manufacturing process for computer chips is such that 5 out of 100 chips are defective. If 100 chips are chosen at random from a box containing 100 newly manufactured chips, what is the probability that none of the chips will be defective? Ex 5: Suppose that of the 20 prospective jurors for a trial, 12 favor the death penalty and 8 do not. If 12 jurors are chosen at random from these 20, what is the probability that 7 of the jurors will favor the death penalty?

Ex 6: Pennsylvania auto license plates have three letters followed by four numbers. If Janie’s initials are J.J.R. and she lives at 1125 Spring Street, what is the probability that the license plate she draws at random will… a) have her initials and house number on it? b) have her initials on it?

Ex 7: Beginning in 1990, General Motors began to use a theft deterrent key on some of its cars. The key has six parts, with three patterns for each part, plus an electronic chip containing a code from 1 to 15. What is the probability that one of these keys selected at random will start a GM car requiring a key of this type?

HW #3: A poll asks voters to rank Social Security, economics, the war on terror, healthcare, and education in the order of importance. a) How many rankings are possible? b) What is the probability that one reply chosen at random has the issues ranked in the order they appear on the survery?

*c) What is the probability that two surveys at random have the same “top 3?”

HW #15: A box of 12 transistors has 3 defective ones. If 2 transistors are drawn from the box together, what is the probability… a) that both transistors are defective?

b) that neither transistor is defective?

c) that one transistor is defective?

HW #33: What is the probability of being dealt a poker hand of 5 cards containing… a) 5 spades? B) 5 cards of the same suit?