Answer:
Two Half-lives
Explanation:
Let number of Parent nuclei Initially present be X,
Then, finally [tex]\frac{X}{4}[/tex] Parent nuclei Will remain with [tex]\frac{3X}{4}[/tex] daughter nuclei.
In one half- life , parent nuclei becomes half of initial.
So, starting with X parent nuclei,
After one half-life, it will degrade to [tex]\frac{X}{2}[/tex] .
After another half life , Parent nuclei will become half of [tex]\frac{X}{2}[/tex]
Which is equal to [tex]\frac{X}{4}[/tex].
So, Parent nuclei have to go through Two half-lives.
