The sample of Carbon-14 after 28,575 years=0.001875 mg
Further explanation
General formulas used in decay:
[tex]\large{\boxed{\bold{N_t=N_0(\dfrac{1}{2})^{T/t\frac{1}{2} }}}[/tex]
T = duration of decay
t 1/2 = half-life
N₀ = the number of initial radioactive atoms
Nt = the number of radioactive atoms left after decaying during T time
Carbon-14 has a half-life of 5715 years, so t1/2=5715 years
A sample today contains 0.060 mg of carbon-14, so No=0.06 mg, then :
[tex]\tt Nt=0.06(\dfrac{1}{2})^{28575/5715}\\\\Nt=0.06(\dfrac{1}{2})^5\\\\Nt=0.001875~mg[/tex]
