3. You roll a fair six-sided die 7 times. What is the probability of getting a) exactly two 4’s?
b) less than (and not equal to) two 4’s? c) two or more 4’s?
this is binary ... four or not four ...
p(f) = 1/6 ... p(n) = 5/6
(n+ f)^7 = n^7 + 7 n^6 f + 21 n^5 f^2 + 35 n^4 f^3 + ... + 7 n f^6 + f^7
a) evaluate the 3rd term ... 21 * (5/6)^5 * (1/6)^5 = ?
b) add the 1st two terms
c) 1 - [result of b)]