Q. If a fair die is rolled 7 times, what is the probability, to the nearest thousandth, of getting exactly 1 two?Answer:
Determine Probability of Two: Determine the probability of rolling a two on a single roll of a fair die. A fair die has six faces, so the probability of rolling any specific number, including a two, is 1 out of 6.
Determine Probability of Not Two: Determine the probability of not rolling a two on a single roll of a fair die. Since there are 5 other outcomes that are not a two, the probability of not rolling a two is 65.
Calculate Probability of One Two in Seven Rolls: Calculate the probability of rolling exactly one two in seven rolls.This event can happen in several different ways: the two can appear on the first roll, the second roll, and so on, up to the seventh roll. For each case, the other six rolls must not be a two.
Use Binomial Probability Formula: Use the binomial probability formula to calculate the probability of exactly one success (rolling a two) in seven trials (rolls).The binomial probability formula is P(X=k)=(kn)⋅(pk)⋅((1−p)(n−k)), where:- P(X=k) is the probability of k successes in n trials,- (kn) is the binomial coefficient,- p is the probability of success on a single trial,- (1−p) is the probability of failure on a single trial.
Plug Values into Formula: Plug the values into the binomial probability formula.Here, n=7 (number of trials), k=1 (number of successes), p=61 (probability of rolling a two), and (1−p)=65 (probability of not rolling a two).P(X=1)=(17)×(61)1×(65)7−1
Calculate Binomial Coefficient: Calculate the binomial coefficient (17).(17) is the number of ways to choose 1 success (rolling a two) out of 7 trials, which is simply 7.
Perform Calculations: Perform the calculations.P(X=1)=7×(61)1×(65)6P(X=1)=7×(61)×(65)6
Calculate Exact Probability: Calculate the exact probability.P(X=1)=7×(61)×(4665615625) (since (65)6=4665615625)P(X=1)=7×(61)×(4665615625)P(X=1)=7×6×4665615625P(X=1)=279936109375
Simplify Fraction and Round: Simplify the fraction and round to the nearest thousandth. P(X=1)≈0.391 (rounded to three decimal places)
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