Starting with 195 grams of a radioactive isotope, how much will be left after 3 half-lives?

Question

The half-life of a radioactive isotope is the time it takes for a quantity of the isotope to be reduced to half its initial mass. Starting with
195
grams of a radioactive isotope, how much will be left after
3
half-lives?

Answer 1

Answer: half of half of half of the original, i.e. 1/8 of the original.