i am reviewing about statistics and probability questions but i do not have answers for it and i am uncertain that my answer done well. Here is the question.
In a test, student have to answer 8 out of 10 questions . How many choices he have if he has to answer at least 3 questions at the first 5 questions?
My answer's goes like this (5C3 x 5C5) + (5C4 x 5C4) + (5C5 x 5C3) = 20 + 25 + 20 = 65 choices
My interpretation for (5C3 x 5C5) is, the student answers 3 question out of 5 first question and for the next part is 5 question answered out of the next 5 question from the second part
I want to ask does my answer valid or it might be wrong? O yeah, i also want to ask, what topics in probability covers this kind of question? Thank you so much