Question

A bag contains 3 red marbles, 2 blue marbles, and 5 green marbles. What is the probability of randomly selecting a blue marble, then without replacing it, randomly selecting a green marble?
A. 1/9
B. 1/6
C. 7/10
D. 4/5

Answer 1

The answer to this is A.) 1/9.

The answer was found as follows:

1. Count all of the total probabilities, make it the denominator of your fraction under your favorable possibilities. In this case, you favorable possibility would be the marble you select, so lets start with the blue marble. But, we would repeat this with the other color later. Now, we have 2/10, or 1/5.

2. After you set up your proportion, do the same for the next marble color. The only difference this time is that because you did not replace that one marble you might've picked up before, your denominator would be nine, subtracting that one marble from your total possibilities. Now you would put your total green marbles over your total possibilities. You should get 5/9.

3. Now, set up both the proportions so you multiply them together, 1/5 x 5/9.

4. Your number now should be 5/45, but we will simplify it to get our final answer of 1/9.