Question: 2016 Fall Final - 24
You repeatedly and independently roll a fair die until the result of the roll is divisible by 3.
Define the random variable $X$ to be the number of times you roll the die. For example, if the
results of the rolls are 4, 5, 1, 4, 3, then $X=5$.
What is the expected value $\mathbb{E}(X)$ of $X$?
What is the expected value $\mathbb{E}(X)$ of $X$?
(a)
3
(b)
2
(c)
5
(d)
4