The half-life of carbon-14 is 5,730 years. How many grams of parent material will remain from a 120-gram sample of carbon-14 after 2 half-lives?

90

60

30

15

Question

The half-life of carbon-14 is 5,730 years. How many grams of parent material will remain from a 120-gram sample of carbon-14 after 2 half-lives?

 90

 60

 30

 15

unklerhaukus · Answer

after each half life the amount of C-12 decreases by half

after two half-lives the amount of C-12 has decreased by half twice,

anonymous · Answer

Thanks

unklerhaukus · Answer

$$120\times\frac 12\times  \frac 12$$

anonymous · Answer

I am looking at the answer as 30

unklerhaukus · Answer

good good

unklerhaukus · Answer

a 120g sample of pure C-14 will be 30g after 11460 years

unklerhaukus · Answer

*i mean C-14  in my first post not C-12.

C-12 is radioactively stable.