Answer:
40.59 years
Explanation:
Use the decay law of radioactivity
[tex]N = N_{0}e^{-\lambda t}[/tex]
Where, λ is the decay constant
λ = 0.6931 / T
where, T is the half life
λ = 0.6931 / 10 = 0.06931 per year
So, N = 6% of N0
[tex]0.06 = e^{-0.06931\times t}[/tex]
By solving we get
t = 40.59 years
