There are 9 orange marbles and 4 green marbles in a bag. One marble is selected at random. What is the probability of NOT selecting a green marble?
- 9 orange marbles
- 4 green marbles
Choose the best answer.
Note
For a “not” event, count the outcomes outside the named event. This is the complement of the event.
- The complement of selecting green is selecting any other color.
- There are 9 non-green marbles out of 13 total marbles.
- So the probability is 9/13 = 9/13.
- A complement probability can also be found by doing 1 minus the probability of the event.
The correct answer is 9/13. This matches the calculation or definition, so students should focus on the reasoning rather than only memorizing the final value.