After a certain lapse of time , fraction of radioactive polonium undecayed is found to be 12.5 % of the initial quantity. What is the duration of this time lapse, if half-life of polonium is 139 days?

Explanation

To solve the problem step by step, we will use the concept of half-life in radioactive decay.

### Step 1: Understand the Given Information
We know that after a certain time, the fraction of undecayed polonium is 12.5% of the initial quantity. This means that if we start with an initial quantity \( N_0 \), the remaining quantity \( N \) after some time \( t \) is:

\[ N = 0.125 N_0 \]
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