Question

7. Suppose that Trevor takes out 1 marble, and holds on to it, then takes out 1 pointanother marble. What is the probability that both marbles will be black inthis situation?

Answer 1

The probability that both marbles will be black is 1/7

Here, we want to get a probability

Firstly, the total number of marbles is 3 + 4 = 7 marbles

Firstly, he takes out 1 marble

The probability that this is black will be the number of black marbles divided by the total number of marbles which is 3/7

Now, in the bag, there would be 6 marbles left and 2 black marbles

The probability of now selecting a black marble would be 2/6

Finally, the probability that both marbles will be black in the situation would be the product of this two probability

We have this as;

`(3)/(7)*(2)/(6)\text{ = }(1)/(7)`