Question

Assume that you are taking a multiple choice test that you have not studied for! The test only has 10 questions and each question has four possible answers. You plan to randomly guess on all 10 questions and the probability you get one correct is the same for all questions. Even though no studying took place, you really want a B. This means you would like to get 8 questions correct. How many combinations exist that yield 8 correct questions

Answer 1

45

Explanation:

To answer this question we will have to use the combination formula.

C(n,r) = n!/(n-r)!r!

n = population set = 10

e = sample set = 8 questions

Inserting into the formula we have:

10!/(10-8)!8!

= 3628800/2x40320

= 3628800/80640

= 45

So in conclusion, we have 45 combinations in existence that would yield 8 correct questions