The sum of the probabilities of all the trials of an events is ______.

Answer

To solve the question "The sum of the probabilities of all the trials of an event is ______," we can follow these steps:

### Step 1: Understand the Concept of Probability
Probability is a measure of the likelihood of an event occurring. It ranges from 0 to 1, where 0 indicates that the event will not occur, and 1 indicates that the event will certainly occur.

**Hint:** Remember that probabilities are expressed as fractions or decimals between 0 and 1.

### Step 2: Identify the Total Probability
When considering all possible outcomes of an event, the sum of the probabilities of all these outcomes must equal 1. This is because one of the outcomes must occur when the event is performed.

**Hint:** Think about a simple event, like flipping a coin. There are two possible outcomes (heads and tails), and the sum of their probabilities equals 1.

### Step 3: Apply the Concept to Trials
For any event with multiple trials or outcomes, if you list all possible outcomes and calculate their individual probabilities, the total of these probabilities will always be 1. For example, if you have three outcomes A, B, and C, the probability of A + probability of B + probability of C = 1.

**Hint:** Visualize this with examples, like rolling a die (1 through 6) or drawing cards from a deck.

### Step 4: Conclusion
Thus, the answer to the question is that the sum of the probabilities of all the trials of an event is 1.

**Final Answer:** The sum of the probabilities of all the trials of an event is **1**.