A radioactive sample has a half-life of 4 years. Calculate the time in which the activity will be reduced to 25%.

Explanation

To solve the problem of determining the time it takes for the activity of a radioactive sample to reduce to 25% of its initial value, given that the half-life is 4 years, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the concept of half-life**:
The half-life (t₁/₂) of a radioactive substance is the time required for half of the radioactive nuclei in a sample to decay. Here, the half-life is given as 4 years.

2. **Determine the fraction of activity**:
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