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Q.
The half-life of ${ }_{84}^{209} P _{0}$ is $103$ years. The time it takes for $100 \,g$ sample of ${ }_{84}^{209} P _{0}$ to decay to $3.125\,g$ is
TS EAMCET 2018
Solution:
In one half life, half of amount is decayed. So, decay occurs as,
So, time taken $=103 \times 5=515\, yr$.
