MATH SOLVE

9 months ago

Q:
# From a collection of 26 exercises, a student knows how to correctly solve 20 of them. If the teacher selects 8 exercises from the aforementioned collection to be the points for an evaluation exam. What is the probability that the exam has exactly 2 questions that the student does not know how to solve?

Accepted Solution

A:

total number of ways of setting the paper = C(26, 8) = 1562275
Number of ways such that students gets exactly 6 known questions and exactly 2 unknown questions
= C(20, 6) x C(6, 2) = 581400
Required probability
$$ =\frac{581400}{1562275}\approx0.37215 $$