Answer: The probability of picking a green marble on the first draw is 4/19, because there are 4 green marbles out of a total of 19 marbles in the bag. Since we're replacing the green marble back into the bag, the probability of picking a brown marble on the second draw is also 1/19, because there is now one brown marble and 19 total marbles in the bag.
To find the probability of both events happening together, we can multiply the probabilities of each event:
P(picking green then brown) = P(picking green) x P(picking brown)
= (4/19) x (1/19)
= 4/361
Therefore, the probability of picking a green marble, replacing it, and then picking a brown marble is 4/361.
Explanation: