Answer:
26150 years
Step-by-step explanation:
First we need to determine the number of half lives -- not years -- it'll take for 100g (of any element) to decay to 3.125 g
First Half Life 100/2 = 50
Seconf Half Life 50/2 = 25
Third Half Life 25/2 = 12.5
Fourth Half Life 12.5/2 = 6.25
Fifth Half Life 6.25/2 = 3.125
So it'll take 5 half lives for 100g to decay to 3.125g.
If the Half Life of Carbon-14 is 5230 and it will take 5 half lives, to determine the number of years we just need to multiply 5*5230
5*5230 = 26150
This means that it will take 26150 years for 100g Carbon-14 to decay to 3.125g.
Hope this helps!