Because you are replacing the marbles then it is an independent event.
P(1st one is not green) = 1 - P(first green),
equally P(2nd one is not green) = 1 - (second green),
Thus it reads P(¬G ^ ¬G) = P(¬G) * P(¬G)
= 15/20 * 15/20
= 225/400
= 9/16
Since the box contains 16 marbles, seven of them white, then the probability of drawing one white marble is 7/16. If you replace the marble and draw again, the probability of drawing another white marble is still 7/16. The net probability of drawing two white marbles, while replacing the first, is 49/256.
5/10
1 in 52
The theoretical probability of randomly picking each color marble is the number of color marbles you have for each color, divided by the total number of marbles. For example, the probability of selecting a red marble is 3/20.
It is 0.2
The probability is 0.3692
There is a probability of 3 that it will be blue.
Since the box contains 16 marbles, seven of them white, then the probability of drawing one white marble is 7/16. If you replace the marble and draw again, the probability of drawing another white marble is still 7/16. The net probability of drawing two white marbles, while replacing the first, is 49/256.
5/10
2/6
The probability is 2/15.
1 in 52
The theoretical probability of randomly picking each color marble is the number of color marbles you have for each color, divided by the total number of marbles. For example, the probability of selecting a red marble is 3/20.
It is 0.2
The probability of picking a green marble from a box that only contains blue marbles is zero.
There are 8 marbles that aren't black, out of a total of 12 marbles, so the probability is 8/12 or 2/3.
We will assume that the bag contains 11 marbles (this is not a trick question!), so 4 are blue and 7 are not blue, so the probability of a color other than blue is 7/11.