The half-life of iodine-123 is 13.2 hours. what percentage of iodine-123 remains in a sample after 36 hours?

The equation for exponential decay, with a half-life of 13.2 hours, elapsed time  in hours,  as the initial amount, and  as the final amount, is    for the final amount, we're interested in what percentage of the final amount is left.  let  be the percentage left, in decimal form.  so the final amount,  , would be equal to  (percent of  , the inital value).    divide both sides by  .    since 36 hours have passed, substitute in     convert 0.1510 to a percent.so 15% of iodine-123 remains after 36 hours.   

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