There are 9 black counters and 9 red counters in a bag. One counter is selected at random. What is the probability of NOT selecting a black counter?
- 9 black counters
- 9 red counters
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 9 non-black counters out of 18 total counters.
- So the probability is 9/18 = 1/2.
- A complement probability can also be found by doing 1 minus the probability of the event.
The correct answer is 1/2. This matches the calculation or definition, so students should focus on the reasoning rather than only memorizing the final value.