📚 Topic Summary
In probability, we often want to know the chance of something not happening. This is called the complement of an event, denoted as P(not event). Since the probability of all possible outcomes must equal 1 (or 100%), we can find P(not event) by subtracting the probability of the event from 1. In mathematical terms, $P(not\ A) = 1 - P(A)$, where $P(A)$ is the probability of event A occurring. This makes calculating the probability of something *not* happening super easy!
For example, if the probability of rolling a 6 on a standard six-sided die is $\frac{1}{6}$, then the probability of *not* rolling a 6 is $1 - \frac{1}{6} = \frac{5}{6}$. These interactive quizzes will help you practice this concept with different scenarios!
🧮 Part A: Vocabulary
Match the terms with their definitions:
| Term |
Definition |
| 1. Probability |
a) All possible results of an experiment. |
| 2. Event |
b) A set of outcomes from an experiment. |
| 3. Outcome |
c) The chance that something will happen. |
| 4. Sample Space |
d) The complement of an event A. |
| 5. Complement |
e) A single result of an experiment. |
(Answers: 1-c, 2-b, 3-e, 4-a, 5-d)
✍️ Part B: Fill in the Blanks
Complete the following paragraph using the words: probability, one, complement, event, subtract.
The probability of an ______ not occurring is known as its ______. To find this, we ______ the event's ______ from ______.
(Answers: event, complement, subtract, probability, one)
🤔 Part C: Critical Thinking
Consider a bag containing 3 red marbles, 2 blue marbles, and 5 green marbles. What is the probability of not picking a blue marble? Explain your reasoning.