There are 4 black marbles and 2 blue marbles in a bag. One marble is selected at random. What is the probability of NOT selecting a black marble?
- 4 black marbles
- 2 blue 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 black is selecting any other color.
- There are 2 non-black marbles out of 6 total marbles.
- So the probability is 2/6 = 1/3.
- A complement probability can also be found by doing 1 minus the probability of the event.
The correct answer is 1/3. This matches the calculation or definition, so students should focus on the reasoning rather than only memorizing the final value.