### Home > MC1 > Chapter 5 > Lesson 5.2.1 > Problem 5-40

A bag of marbles contains only the colors red and green.

If the probability of getting a red marble is

, what is the probability of getting a green marble? The probability stated means that if there are

marbles in the bag, there is only one chance that you will pull out a red marble. How many chances are there that you will pull out a green marble? If there were only three marbles in the bag, and one of them is red, then the other

must be green. This means that out of marbles are green, so the probability must be Another way to think of this is that if

of every marbles is red, then the other of every must be green. If there are

marbles in the bag, how many are green? If the probability of picking a green marble is two-thirds, that means two-thirds of the marbles are green. What is two-thirds of

? How could you represent two-thirds in a fraction with the denominator, or bottom number, of

? The numerator, or number on top, will be the number of green marbles.