If the half-life of a radioisotope is 10,000 years, the amount remaining after 20,000 years is
none
half
a fourth
double
answer is c

Considering the half-life of 10,000 years, after 20,000 years we will have a fourth of the remaining amount.

Explanation:

The half-time is the time a radioisotope takes to decay and lose half of its mass. Therefore, we can make the following scheme to know the amount remaining after a period of time:

Time Amount

t=0x

t=10,000 yearsx/2

t=20,000 yearsx/4

During the first 10,000 years the radioisotope lost half of its mass. After 10,000 years more (which means 2 half-lives), the remaining amount also lost half of its mass. Therefore, after 20,000 years, the we will have a fourth of the initial amount.

your answer would be a. 12.5 kg

the answer is b & c i believe : )