Answer:
t = 2.6 billion years
Explanation:
If potassium becomes 25% of its initial value
so we can say it becomes half two times
as we know that 25% means it is 1/4 times of initial value
so we will have
[tex]N = N_o e^{-\lambda t}[/tex]
here we know that
[tex]N = 0.25 N_o[/tex]
[tex]0.25 = e^{-\lmabda t}[/tex]
[tex]ln 4 = (\frac{ln 2}{T_{1/2}}) t[/tex]
[tex]t = 2 T_{1/2}[/tex]
[tex]t = 2(1.3 billion \: years)[/tex]
t = 2.6 billion years
