What percentage of decay takes place in the average life of a substance ?

Options

A. `63.21%`
B. `36.79%`
C. `90%`
D. `99%`

Answer

To solve the question of what percentage of decay takes place in the average life of a substance, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Average Life**:
The average life (or mean life) of a radioactive substance is the time taken for the substance to decay to 36.7% of its original amount.

2. **Determine the Remaining Percentage**:
If the average life of a substance results in it decaying to 36.7% of its original amount, we can calculate the percentage that has decayed.

3. **Calculate the Decayed Percentage**:
The total percentage of the substance is 100%. Therefore, the percentage that has decayed can be calculated as:
\[ \text{Decayed Percentage} = 100\% - \text{Remaining Percentage} \]
Substituting the remaining percentage:
\[ \text{Decayed Percentage} = 100\% - 36.7\% = 63.3\% \]

4. **Final Answer**:
Thus, the percentage of decay that takes place in the average life of a substance is approximately **63.3%**.