Q. If a fair die is rolled 6 times, what is the probability, to the nearest thousandth, of getting exactly 4 sixes?Answer:
Identify type of probability problem: Identify the type of probability problem.We are dealing with a binomial probability problem because we have a fixed number of independent trials (rolling a die 6 times), two possible outcomes (rolling a six or not rolling a six), and we want to find the probability of getting a specific number of successes (rolling exactly 4 sixes).
Calculate probability of success: Calculate the probability of success on a single trial.The probability of rolling a six on a fair die is 61, since there are 6 sides and only one of them is a six.
Calculate probability of failure: Calculate the probability of failure on a single trial. The probability of not rolling a six (failure) is 65, since there are 5 sides that are not a six.
Determine number of ways: Determine the number of ways to choose 4 successes in 6 trials.We use the combination formula to find the number of ways to choose 4 successes (rolling a six) out of 6 trials, which is denoted as "6 choose 4" or C(6,4).C(6,4)=4!∗(6−4)!6!=((4∗3∗2∗1)∗(2∗1))(6∗5∗4∗3∗2∗1)=(2∗1)(6∗5)=15
Use binomial probability formula: Use the binomial probability formula to calculate the probability of exactly 4 sixes in 6 rolls.The binomial probability formula is P(X=k)=C(n,k)⋅(pk)⋅((1−p)(n−k)), where P(X=k) is the probability of k successes in n trials, C(n,k) is the number of combinations, p is the probability of success, and (1−p) is the probability of failure.P(X=4)=C(6,4)⋅(61)4⋅(65)(6−4)P(X=4)=15⋅(61)4⋅(65)2P(X=4)=15⋅(12961)⋅(3625)P(X=k)0P(X=k)1P(X=k)2 (rounded to the nearest thousandth)
More problems from Probability of independent and dependent events