12 posters for 36 student;21 poster for 63 students
1 answer:
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Answer:
0.173 probability that she gets exactly three questions correct.
Step-by-step explanation:
For each question, there are only two possible outcomes. Either she guesses the correct answer, or she does not. The probability of guessing the correct answer for a question is independent of other questions. So we use the binomial probability distribution to solve this question.
Binomial probability distribution
The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.
In which is the number of different combinations of x objects from a set of n elements, given by the following formula.
And p is the probability of X happening.
Seven questions:
This means that
Each question has four choices.
Abby guesses, which means that
Find the probability to the nearest thousandth, that Abby gets exactly three questions correct.
This is P(X = 3).