A student has a bag of marbles. There are 5 pink, 7 red, 12 green, 2 blue, and 4 black marbles in the bag. Calculate the theoretical probability of picking a green marble.
The total number of marbles in the bag is 5 + 7 + 12 + 2 + 4 = 30.
The number of green marbles is 12.
Therefore, the theoretical probability of picking a green marble is 12/30 = 2/5 = 0.4 or 40%.