A bag contains 3 pink marbles, 4 orange marbles, 2 black marbles, and 4 green marbles. If 4 marbles are selected, what is the probability of picking 4 green marbles?

There are LaTeX: \displaystyle C(13,4)=715 to select 4 marbles. There are LaTeX: \displaystyle 1 ways to select 4 green from 4 green. This gives the probability LaTeX: \displaystyle \frac{1}{715}