Answer:
1758 years
Step-by-step explanation:
0.693/t1/2 = 2.303/t log No/N
t1/2 = half life of the C-14
t= time taken
No= amount of radioactive material originally present
N= amount of isotope after time t.
But N= 0.81 No
0.693/5715= 2.303/t log No/0.81No
0.00012 = 0.211/t
t =0.211 /0.00012
t= 1758 years