The rate of decomposition of radioactive radium is proportional to the amount present at any time. The half-life of radioactive radium is 1599 years. What percent of a present amount will remain after 635 years

Explanation:

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In this case, since the kinetics of the radioactive decay is assumed to be first-order, it is possible to use the following equation to quantify that change:

Thus, given the elapsed time, 635 years, and the half-life, 1599 years, we can compute the fraction of the present amount:

Thus, the percent is:

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the answer to your question is c