# Math Help - probability problem

1. ## probability problem

Mr. Johnson gives his class a list of 20 study questions from which he will select 8 to be answered on the final exam. If a student knows how to answer 14 of the 20 questions, what is the probability the student will be able to answer correctly:
a) all 8 questions
b) exactly 5 questions
c) at least 6 questions

Mr. Johnson gives his class a list of 20 study questions from which he will select 8 to be answered on the final exam. If a student knows how to answer 14 of the 20 questions, what is the probability the student will be able to answer correctly:
a) all 8 questions
b) exactly 5 questions
c) at least 6 questions

use Bernoulli Trials (the binomial distribution) with n = 8 and p = 14/20 = 7/10

3. You can use a binomial probability.

For the second one, p=14/20=.70, q=1-p, k=5, n=8

$C(n,k)p^{k}q^{n-k}$

$C(8,5)(0.7)^{5}(0.3)^{3}$

You can adjust accordingly on the others.