Answer:
Explanation:
Half-life is the time for a sample reduce its amount to the half.
The radioactie isotopes, such as radon-222, have constant half-life times.
The amount that remains after a number, n, of half-lives may be calcualted by the following exponential decay equation:
[tex]A=A_0[\frac{1}{2}]^n[/tex]
From which you get:
[tex]\frac{A}{A_0}=[\frac{1}{2}]^n[/tex]
Here, you want A/A₀ = 1/4
So, you just must to solve for n:
[tex]\frac{1}{4}=[\frac{1}{2}]^n\\ \\ \frac{1}{2^2}=\frac{1}{2^n}\\ \\ n=2[/tex]
Then, two half-lives will have passed, which equals to 2×3.824 days = 7.648 days.
