A certain radioactive isotope has a half-life of 4.0 hours.How much time does it take for the amount of the isotope to decrease to one-eighth of its initial amount?

Name: A certain radioactive isotope has a half-life of 4.0 hours.How much time does it take for the amount of the isotope to decrease to one-eighth of its initial amount?
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Quizplus · Accepted Answer

The amount decreases to one-eighth, which means it goes through three half-lives (since $2^3 = 8$). Since each half-life is 4.0 hours, it takes $3 \times 4.0 = 12$ hours.

A Certain Radioactive Isotope Has a Half-Life of 4