Determine the amount of time it takes for three fourths of a radioactive sample of an isotope to decay?

Answer 1

The half-life is 4 days. That means half of it will be gone in 4 days, and that leaves half of the original sample. In another 4 days, half of the remaining half will have decayed. And that will leave only 1/4 th of the original sample. That means 3/4 ths of the original sample will have decayed. In 8 days, three fourths of a sample of a radioactive element with a half-life of 4 days will have decayed.

Answer 2

I would take two half-lives for a radionuclide to decay to one fourth its original activity. In one half-life, it decays to one half. In the next half-life, it decays to one half of that one half, i.e. one quarter. In the next half life, it decays to one half of the one half of the one half, i.e. one eighth.

Answer 3

One half-life leaves one half of the original. Two half-lives leaves one half of the one half, i.e. one quarter of the original. So, two half-lives decays three quarters, leaving one quarter.

Answer 4

It's half-life.

Answer 5

2

Answer 6

2